OP said
OP already has one of the most potent of the 340 lineage, and the headers allow that factory cam to finally wake up. The engine combo is already as good as it gets for;
, short of spending a few thousands of dollars.
@Gtsjosh
You're gonna get a lot of varying opinions in this thread, and in the end you will have to sort thru them and search for the nuggets.
My best advice is to abandon this thread and come back with something like this;
then add;
"I have *** amount of dollars to spend; where should I begin?
I can almost guarantee that most of the answers will actually make sense
=================
I'll give you my answer right now;
install the tallest widest tires that FILL those tubs, on appropriate wheels; Move the springs and narrow the rear if you need to. Get some HD street springs and probably slapper bars. Then, if you have a regular A833 with the 2.66low, put the biggest number rear gears in the housing, (Up to 4.10s) that you can stand to cruise with, and don't forget the sure-grip. If you already have gears back there between 3.55 and 3.91, then I suggest to consider swapping it out in favor of the 3.09 Commando. See Note-1
Now, put some disc brakes on the beast, if it doesn't already have the Rally Suspension package.
That is where this road starts.
If you don't start here^^,
and DO build your engine up to 400hp;
you will be driving one of the World's fastest skateboards. That is to say; it won't stop, won't steer, won't handle, will be very little quicker in the zero to 60 contest, and it will scare the crap out of you just about every time you lay on the gas for 5 or 6 seconds.
But you will be able to scare thechit out of all your friends, until no one will ride with you any more. After that, it will get very lonely......
Note-1
For the funnest streeter, you want to be able to hit about 60/65 in second gear. If you have to shift into third, that will put your engine off the cam, and reduce your average power, which will then be slower in the zero to 60 contest. If you don't hit at least 4800, you might as well install a 318 cam.
Your 1968 cam, if still in there, specs out at 276/284/114 and that means the power-peak will be up around 5200, and with the right springs you can rev that to whatever. 5400 sounds good to me, to start with.
That means to top out at 60mph/5400 in 1.92 second gear with 28" tires (about the tallest you can fit), would take 3.91s.
And 3.91s will make a starter gear of 10.40, normalized to 8.91 at 24", Not great but adequate. But 65= 3050 so that might put a damper on your cruising. However, on short hops, 10% lower rpm only takes 10% longer to reach your destination. I burned up a lotta lotta miles at 56mph.
Just for comparison; if you have 3.23s; you will hit 60mph at only 4465 assuming no tirespin, with those 28s.
But it's worse; 32mph in Second (still with 3.23s) will be 2380. Downshifting into 2.66 low will get you
3500/no tirespin with slapper bars, and that is waaaaaaaay off the power.
Whereas 3.91s would get you
4000 perhaps some tirespin; and the
309 Commando low gear would get you
4640 with raging tirespin.
The point is, with a given engine, matching the combo to the application is King, and Torque multiplication will get you a lotta lotta fun.
If your budget is limited, I would suggest starting with;
installing the largest tires that fit in the stock tubs, a well-adjusted SureGrip, slapper bars, and whatever gears will get you the 8.91ish normalized starter gear.
