Building the best bang for the buck ????

[71 chevy]

6.0 ls1 with with twins would run around 5k and has run 8.7s to 8.9s in cars ranging from 3000lbs to 3300lbs.

Most people use an aftermarket engine management(megasquirt, FAST, etc.)? or stock or even blow through carb ?

yes.

i kid. most i see use hptuners or efilive with the stock computer

[572 BBC]

I'll chime in with everyone suggesting a BBC.
Buy lots of used stuff. Safe stuff like intakes, ignition, carbs and water pumps. Heads and valve train if you're careful (lucky).
Yellow Bullet and Racing Junk are full of this kind of stuff..
Find a useable bolck and have the machine work done yourself, so you will know what you have.
Buy the serious, expensive stuff new. Rotating assembly, cam shaft, etc..
It's cheper to buy good stuff once than to replace the cheap stuff later; but don't spend money buying better stuff than you need.

Take a lesson from me. Decide what you are building before you start and stick with it.
Race cars are a lot like wives. Expensive and noisy to have around. But realy expensive to change your mind about what you want.

Having said all that; who wants my extra stuff? (Wife said to be specific: The BBC parts.)

oh holy crap isnt that all true!!!!!!!!!!!! BIG CHEVY WITH A BIG SHOT OR TWO :)