1991 Chevy Camaro Replacing the engine

You didn't say what year motor you have. (L-98, LT-1, etc.) But it will bolt in with no problems.

However, the tbi will have to be reprogrammed for sure.
If it's a LT-1 motor, then you'll need an all new computer, fuel injection, ignition control, etc.

If it's an L-98 motor, then all you'll need to do is reprogram the computer to compensate for the extra cubic inches.

If you were to by a 1991 L-98 350-cubic inch engine, then you could basically keep everything you have, but the computer would definitely have to be reprogramed.

It won't be able to compensate for the larger air/fuel demands of that motor.

Also, you may have to use larger injectors (Higher flowing) Other than that, small block motors of that era have completely interchangeable parts (External)

Now, it you buy an LT-1, you'll have to changed everything. You'll need to buy the computer, wiring harness, fuel and ignition system to go along with the motor.

Unless you are already familiar with that engine swap combo, I'd suggest you have a shop do an LT-1 swap.