I have a 1991 RS Camaro. I am going to put an older 350 (that is slightly modified in it.) The motor is a 1975. I know I have heard that there is a way to get the TBI to bolt up to the old motors. I know that the older 350 will bolt up to everything else but how do I get the TBI to bolt up to it?

 

If you're using the old heads, you'll have a problem with the middle two bolt holes on each side of the intake. On some manifolds , you can just grind the holes a little bigger to make room.
The driver's side dipstick may give you problems, depending on which headers or exhaust manifolds you use.
Also, the flywheel or flexplate will have to be for the early-style two-piece rear main seal.
Those are the only major difficulties I can think of, off the top of my head.
You might be better off using a four-barrel carb intake made for the older heads and use an adapter for the TBI. Holley and others make adapters for a reasonable price. I hear PAW has adapters for less than $10.
You'll need 350 injectors, knock sensor and ESC module if swapping 350 in place of 305.

-Rich-