I've been working on some VIN number crunching. This is a production breakdown for the 82 model year. I don't have the complete list of all cars but I have a sample size of 83%. That means I can calculate to within about a percent or so. Don't take these numbers as the absolute exact truth but a really, really good approximation. Special thanks to Kizz for getting me started. Results are in percent of total production.

First off, here's the engine codes
F= 2.8L 173 CID (LQ8) carburated, export only
2 = 2.5L 151 CID (LQ9)
1 = 2.8L 173 CID (LC1)
H = 5.0L 305 CID (LG4)
7 = 5.0L 305 CID (LU5)

Firebird Base Mod
Norwood (LQ8)=0.25%
Norwood (LQ9)=4.20%
Norwood (LC1)=8.56%
Norwood (LG4)=0.52%
Van Nuys (LQ8)=0.04%
Van Nuys (LQ9)=8.85%
Van Nuys (LC1)=10.70%
Van Nuys (LG4)=1.85%

Trans Am
Norwood (LU5)=3.27%
Norwood (LG4)=10.75%
Van Nuys (LU5)=8.08%
Van Nuys (LG4)=24.18%

S/E
Norwood (LQ8)=0.01%
Norwood (LQ9)=0.31%
Norwood (LC1)=4.09%
Norwood (LG4)=1.48%
Van Nuys (LQ8)=0.00% (i know of only 2, so it got rounded down to 0)
Van Nuys (LQ9)=0.74%
Van Nuys (LC1)=6.03%
Van Nuys (LG4)=6.12%