'65 Barracuda 318 LA Transmission Questions

Wasn't too sure where to post this, but I'm just about ready to start working on my '65 Barracuda and I'm trying to get a few things together. I'm thinking of throwing in a 318 LA engine, and I'm trying to figure out what transmission to go for. I'm wanting something manual, and I have ZERO knowledge on what transmission to use, work required, etc. I don't want a crazy HP number, maybe 350-400 max, so any transmission capable of handling 400 should be fine, right? I also wonder how hard it would be to come up with a floor shift setup? Something suitable for highway cruising? The car was originally a 273 with an automatic, but I've decided to start from scratch. I've done some reading on the A833 transmission, but I have no idea if that'd bolt up to a 318 LA motor.
I haven't done much wrenching, but surely it can't be that hard! Besides, there's no time to learn like the present. Any info would be appreciated, thanks.

318 LA block will bolt right up to an A833 with the proper bell housing. Converting an auto body to manual will be more involved. There are Threads here on FABO that can help. 65'

400 from 318cubes, for the street; is IMO crazy .( It's even hard for a 360.) You're looking at 1.26 hp per cube, so she will have to be a high-rpm engine to get there. That means you'll need to carefully co-ordinate all your parts,specialized machining, and it'll probably be cheaper to use aftermarket ported heads, than to use the factory LA stuff. Headers will be mandatory, as well as a big cam with lots of overlap.
The thing is; at 3000pounds, you only need 300 to have fun with. And that is .94 hp per cube and is much easier and cheaper to do. Any Mopar trans can handle that.
A basic 360 at .94hp per cube is ~340 hp and makes a killer early-A.

65 Barracuda’s are small. You can’t get a lot of tire in the rear wheel wells and you have to do some cutting to fit a 727 auto in. That leaves an A833 4 speed or a 904 auto. Either is capable of holding a nice 318. For street use, 320 to 340 hp is plenty. You will also need to upgrade the rear unless it has been done. I personally would do the 273.

You will likely need a new driveshaft too since 1965 was the last year for the ball & trunion "Detroit" fwd U-joint. Engines 1968+ (or so) have a larger crankshaft hole for the transmission torque converter snout, so need a spacer. Not an issue if the trans is similar year as engine. I haven't fooled w/ manual trannys, but recall reading that the crankshaft has to be deep enough for the pilot bearing, which might not have been true if the engine was came w/ an automatic. Don't quote me, but research.

AJ/FormS said:

400 from 318cubes, for the street; is IMO crazy .( It's even hard for a 360.) You're looking at 1.26 hp per cube, so she will have to be a high-rpm engine to get there. That means you'll need to carefully co-ordinate all your parts,specialized machining, and it'll probably be cheaper to use aftermarket ported heads, than to use the factory LA stuff. Headers will be mandatory, as well as a big cam with lots of overlap.
The thing is; at 3000pounds, you only need 300 to have fun with. And that is .94 hp per cube and is much easier and cheaper to do. Any Mopar trans can handle that.
A basic 360 at .94hp per cube is ~340 hp and makes a killer early-A.

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You're right, I didn't take into account how light the car is! After some looking, I found a bunch of motors locally for really good prices. I suppose a 360 would be a really good budget option, plus I wouldn't have to do anything about the heads. Thanks for the info!

If you get a chance to get an early Magnum;88 to 92,jump on it. These are pretty good building blocks. The decks are a lil lower, and they are born with higher compression, and "they say", the stock Magnum heads are better than any stock LA heads. An extra bonus is you can run LA heads on those early blocks, because "they say" those early blocks are drilled for rocker-shaft oiling, if you happen to have a nice set of LA heads.. A low mileage unit, could be a drop-in. If you never expect to run LA heads, then a newer one is, I suppose, better.And a supper bonus is the roller cam.
I say "they say" because I am repeating what I heard on FABO and have no personal knowledge. It is just an option.
About the only drawback to Magnums, is you will need a new intake, and an LA front end, if yours comes with a serpentine front. And "they say" truck blocks need to have the truck mounts slightly shaved to fit headers.
As to headers, if it was me I would get the type that pass a couple of the pipes thru the aprons, leaving more room in the tight tunnel;if it was me. With the stock cam. I suppose headers could be optional . But any cam with over ~40* of overlap, is gonna benefit from headers. By 45* you are sacrificing a fair bit of power and torque.
5.9 Magnums are, from the factory, already fairly powerful. And just by adding headers,a 4bbl,and fresh cold air; you might already by close to or over 300hp, and they are docile long-distance runners too. Just be sure to give them a free-flowing exhaust, especially the front half. Make sure you run it at over 180*; And I recommend working up to 200*, keeping up with the tune.
As to the transmissions;
The stock Magnum cam,IIRC, was a 252/112; so it has a fairly wide powerband. Therefore,I would gravitate towards the A999, or it's sister the A998. Both of these can be had with the 2.74-1.54-1.00 ratios, This 2.74 first gear could allow you to run a lower rear gear, for a lower hiway rpm, without sacrificing take off, as compared to the A904 with ratios of 2.45-1.45-1.00.... For example;the A904 with 2.45x3.55=8.70, while the A998 with 2.74x3.23=8.85. The rpm difference at 65 mph, is 9% lower with the 3.23s or about 265 rpm, if that matters to you. If not, then the early gear-set is a better fit, if you expect to swap cams later, or install any cam with a lesser LSA than 112.
By 1971 the A904 was pretty much perfected. But there is one better option . The early A998s IIRC, came with the A904 ratios, but had HD guts. But it also could be had with a loc-up convertor, which is maybe OK for the stock 5.9, but IDK if it would survive 300plus or for how long. So, IMO I would avoid a Loc-up A998. You cannot mix and match convertors; the inputs between loc-up and non loc-up are different; so get the right one the first time. Usually the trans type is cast onto the topside of the bellhousing, but "they say", not always. If not, then you'll have to figure it out.

65 is the wrong chassis to learn transplants and big power engines. Really, it is so restricted on headers and space that keeping the stock auto and maybe getting a higher numeric rear and a higher RPM cam profile would get you into the fun zone with a minimal learning curve. 273/4 or even a cheaper 67 318 can rev hard with a 4bbl intake and dual exhaust. If you like to shift, go full manual valve body. Sticks require a manual hump, Z-bar stud, 3-pedal setup and you should address the rather weak 7.25 rear for a stick application. It can be done manually but an auto is so much easier. 360 is the same size as a 273 dimensionally and the bigger 340 logs will fit manual steering just fine. Headers are out there but are >$800.