I bought a Firebird last year for $500 with 3000 miles on a rebuilt 350. Drove it into the garage and tore it out. Small block chevies are all over the place. If you've got a TH400, stick with it. If you've got a two speed, look for a 700R4 (may involve moving the trans crossmember) or a TH350 or 400.
Of course, if you can't tell how many times your truck shifts, an engine swap may be out of your ability range. Not trying to be a jerk--just make sure you can handle the job. Call your buddies and bribe with beer. It's a weekend job for two guys with the right tools.
