The car with the 350 motor is either a LeSabre or a roadmaster. Will this engine fit well or will modifications need to be made? Also if transmission is switched should it work with the rest of the original chevrolet parts in the camaro?

Also will the engine run differently than if I use a rebuilt chevrolet 5.7L?

They are basically the same engine externally.

The transmission will be missing the torque arm mount on the tailshaft housing. 4 bolts, switch them around.

Woa, I thought someone was putting a 350 into a LeSabre.....

Yeah the 350 from the Roadmaster would bolt exactly where your 305 was. But I would think that you would need the computer from the roadmaster also, for the 350 throttle body injection, unless you plan on putting a carb on it. I would think that the Roadmaster computer can plug right into where your existing computer is tho.

The longblock is pretty much "plug and play", however the center intake manifold bolts are angled differently, which will require you to modifiy those bolt holes in the intake (assuming you are keeping your original intake).

LT1 or TBI 5.7???