Hi, I have an 83 firebird with a 305 thats on its last leg. I have a rebuilt buick 350 from a 78 lesable sitting around, and I was just wondering if it would fit? I think the trannys are the same, im just worried that the moter mount locations wont line up or Ill have trouble hooking up the exhaust. If someone could help, Id appreciate it greatly?

The trans is not the same. The bolt pattern on it matches a Chevrolet block, not a Buick block. Exhaust is completely different, mounts are completely different. Unless of course, your Lesabre had a Chevy 350 rather than a Buick one; but while not impossible, that isn't too likely.

Probably not a good swap, especially not to put some gutless 70s smog motor in there. Now if you had a 455 out of a 70 Skylark GS it might be worth the effort, but not that one.

Gaa! So what your saying is that the pontiac engine in a firebird uses a chevy rather than a BOP Bellhousing pattern? Also, if the mounts wont line up, Does anyone know how much it would cost to take it to a machine shop and have them make it line up? thanks

The engine in your firebird (if stock) is a chevy V-8 not a pontiac. All third gens came with chevy v-8's regardless if it is a chevy or pontiac.

Yet, figured that out today. I think what Im gonna do is just replace the valve stems and top end gaskets, and put a mallory ignition on. The problem was that it was only firing on 7 cylinders and would stall out occationally, and is spitting out black smoke. Anyway, Anyone know where I could sell a 350 buick?

You'ld need a BOP trans and 350 buick mounts.
A 350 buick SHOULD fit as long as you use your cast iron manifolds and not headers (I've seen a couple of 455 buick/thirdgen swaps).
Pontiac motors were never installed in thirdgens just SB chevys, the last pontiac motor that was installed in an f-body was the 301 in '81.
If your still interested in putting your 350 Bew in go to the TA Performance website, they've got all kinds of high-perf parts for the 350.