Here is the what I found for powerplant setups from 80-87 on Regals (no T's or GN's), 80 4.3, 4.9 5.0, 3.8 (A) all 2 & 4 bbl carb., 81= 4.4 4.3 3.8, 82= 82 & 83 = 4.3 & 5.7 DIESEL, 4.1 4bbl, 3.8 2bbl, 84= 4.3 MPFI, 3.8A 2bbl, 85= 4.3-5.7diesel, 3.8 2bbl, 86= 5.0 4bbl 3.8 2bbl, 87 5.04bbl, 3.82bbl plus our beloved vin 7 (which means it was only an "option" for Regal minus the T-Type and GN id's) What took place in that time period was American car makers scrambling to meet CAFE and emission standards that they thought would never happen. Just because they had diesels available it didn't mean they had to sell em. Sidebar - I had a little old lady customer that had a 79 Turbo Riviera, I loved that car. You really got to appreciate turbo lag.