265 to 403 engine swap

I have an '81 firebird with the original 265ci (4.3L) V8 and a THM250 transmission. The car is in great condition, but the engine has been leaking oil from every seal, and probably isn't worth rebuilding.

I have already pulled the engine out, and I've been looking around for replacement engines and transmission that I might be able to swap in. I ran across a complete 403ci (6.6L) engine and THM350 transmission from a '79 Trans Am for a reasonable price, and I'm trying to find out how difficult of a swap that would be. Will I be able to buy the correct motor mounts and drop the new engine and tranny right in, or will this require some major cutting and welding?

I would appreciate any advice on this... thanks.

You might have to make (or have someone) motor mounts. There should not be any cutting involved. Other than that you might need a new x-member. Good luck.

That I can probably handle. It turns out that I'm getting just about everything under the hood, as well as the exhaust and suspension parts from the '79, so that should give me quite a bit to work with.

Thanks for the reply.