Help on rebuilding a 73 340

Yes and no.
Generally; the cam, the cr, the TC and the rear gears, are more than engaged, but not married. And the cam has the greatest influence.
See, the engine can be built to operate anywhere from idle to around 7000 rpm. With deep pockets a little higher. The thing is, its the cam that more or less controls the operating range.And it has a fairly narrow window in which it likes to operate.So if you select a cam that likes to run at higher rpms, you have to get the rpms up to that rpm, which is easy in neutral. But if its stuck pulling 3500 pounds up to it, its a fair bit slow at it.
So the solution is to figure out how to let the engine get up to its happy zone.
This is done,in an automatic car through the Torque Convertor(TC). By letting it be lazy at lower rpms, it scoots up to the happy place, in a heartbeat or less.And then the car blasts off.
Rear gears, or actually a combination of rear and trans first gear can also play a strong role in blasting off, and need to be synchronized with the TC selection.
To get a sense of this,Imagine your teener with 5.13 rear gears and a stock TC.Imagine hitting the gaspedal with that. The little teener would blast off the line.Next imagine that same teener with 2.76 rear gears.Acceleration off the line and through the lower rpms is kinda mundane.
Next,imagine your stock teener with a 3000 stall TC and the 2.76 gears.When you gas it the rpm would zip up to where the engine has some decent torque, and away the car goes. Then imagine her,still with the 276s but now with a 1000rpm stall TC.The stock teener has good low rpm torque, but this TC would spell S-L-O-W.
Now, finally imagine your teener with a combination of various gears and stalls.
The engine will get your vehicle moving with any gears, and TC,and cam.Its just that when these parts are matched,it does it quicker.
This whole discussion revolves around just one aspect of your motoring experience.
Other things to consider are: do you even care if it takes 2 or 3 seconds longer to get up to highway speed? Are you more concerned about how much it costs to drive a hundred miles? Is it a city car, a highway car, or some combination.If you get your car to attain 100mph in the QT, do you care how long it takes? Will you be the only driver?
There are dozens of such questions that need to be answered on every build.You kinda need to sit down, and list the must-haves, in order of importance, so that sacrifices can be made.
There are always sacrifices, or at least compromises.Thats why I say run what you brung. You already have the parts.Perhaps these parts will suit your driving experience. But if not, you can make a much more informed decision as to what parts to replace, and in what order.
If you cornered me as to just one thing now.It would very clearly be the cam choice.All your other decisions will be affected by it.And judging by the tone of your questions,I would suggest caution.Two sizes too small is way more liveable, on the street, than one size too big.Especially if your tuning skills,and/or time,are limited.
Sincerely, AJ