Rear ends

5-speed manuals, to suffer 360 torque,are not cheap!
And you can't stuff much tire into a factory 70 Dart rear tub.
With a modest well-engineered 360, IMO,a 5-speed is not needed for street duty.
A good combination is the 3.09-1.91-1.39-1.00 box and 3.55s,for city work or same box and 3.23s for regular hiway use.
The 3.55s will get you about 65=5500 in second gear.
Then just build an engine to make peak power at about 300 under that rpm, and you will have a killer combo.
But to be quick, you are gonna need a traction aider, cuz in that Swinger with 255s, the tires will not hook.
Or you can build the bottom end power slightly soft.
IMO, it is near madness to build a near 500hp fire-breathing engine, that just smokes the tires all the way to 65 mph. Unless of course that is what you built it for,lol. But an engine like that costs money. It costs you in the build, the maintenance, parts attrition, and of coarse at the gas-pumps.
IMO, it is better to build the engine to a power level that the tires,the chassis, and your pocket book, can handle.
Not buying tires at the start of every season is nice.Driving a week on the same tankful is nice. Not having to re-set your valve lash, at the end of the summer is nice. Remembering in spring, halfway thru the resetting, that you already did this last fall;is not nice. Not worrying about blowing up that monster motor,is nice. Having the powertrain survive,year after year, is nice. Accumulating 12,000 miles a year, with nothing but normal maintenance, is really really nice.
Putting in a new clutch twice in one summer is not nice. Blowing up the tranny is not nice. Nor is twisting off a driveshaft, or dropping teeth off the ring gear. Nor spinning the pumpkin around the axle tubes.
Getting sideways on the 1-2 shift, mounting the boulevard facing backwards, watching traffic go by, is embarrassing. Worse is getting back down and realizing one of your rear tires is no longer round, and there is no air in it.
Slamming into a corner to fast, and sliding across three lanes, mounting the curb, and blowing two tires, is what can happen with too much power and/or too little tire.
Whatever you do, do not install an 11,000 rpm MonsterTach with 3 lites hanging off the side to tell you when to shift, when it's over-revved , and when to wipe your azz. That is soooooo tuner-ridiculous.IMO.
So, what is AJ running on about now?
Common sense is what.
If you got the bucks do whatever you please, but put some decent tires under the most evil handling factory stock A-body, Chrysler ever built.Put three or even four thousand into the suspension,steering,brakes,and tires, before you ever slide the engine in. Your life may depend on it. I mean the car is now 47 years old, and it was a terrible handling car on the day it was born.
If you're not made of money,try and use some common sense. That chassis couldn't handle the powerhouse 340 of it's day.
Thank goodness the Swinger 340 came with disc brakes; they saved my 17 year old azz so many times. And a few times not.
One thing I learned was that all the brakes in the world are useless if the car is not on the ground, or if it is sliding sideways. A second thing I learned is that PolyGlass tires are like ball bearings when going sideways. And not much better when oriented properly.