Simon, here in the states, I think the base Camaro/Firebirds had the 3.8L V6. Maybe Europe got the smaller GM V6s?
Anyhoo, the Monogram 1/24 Buick Regal GN would get you a 3.8L, set up in rear-drive configuration you need for an F-body.
The old MPC Beretta GT/GTU (not GTZ, which had a QUAD-4) kit had the 2.8L V6, but in front-drive configuration. Revell Pontiac Grand Prix also had the lil' V6s, in front-drive also.