Does anyone know of a source where there is a computer model where you can model expected RPMs and torque for a variety of engine, transmission, and differential options?

I have two engines I can use on my 50 Chevy. A 350 or a 302. I also have a 350 and a 700 auto trannies. I have a more modern rear end but am wondering if its right for what we want to use it for. I still need to determine its gear ratio.

Given these potential options I have, I wanted to see what a computer model would tell me is the best choice.

I am new at this so BE KIND! LOL