can a 1979 firebird oldsmobile 403 fit into a 1978 camaro that had a chevy 350, can it bolt right up to a th350 the camaro has now and bolt up to the engine mounts that the 350 bolted into.

 

I think you would have to get the correct motor mounts. I don't know if they're the same or not. You might have to get them for a Firebird with the 403 Olds engine. The Firebird and Camaro frames should be the same.

The 403 Olds uses the "BOP" (Buick, Olds, Pontiac) bell housing bolt pattern which is different from the Chevy bell housing bolt pattern. I've seen adapter plates that allows the use of the "BOP" tranny's with a Chevy engine. I don't know if it can be used the other way around or not. Look at Trans Dapt. They make a bunch of different mounting plates and adapters.

Just out of curiosity, why a 403 Olds?

 

The trans will bolt up, but not with all the bolts. The alignment pins are std. for all GM TH350 and TH400 trannys, but usually only two bolts on each side line up perfectly. The others can easily be adapted without a kit by making a bushing with a tab. Take a piece of solid round stock and bolt it to the block, then use a 3/16" tab to overlap the tranny and bolt through it. Tack weld the two together, and remove to finish welding.
Frame mounts from a donor car can be chopped off, mounted to the engine and drop in your car. Then tack weld them once it's level, and pull the engine to complete the welds again.