how come the Series III 3800 isnt available in a Bonneville but is on a Grand Prix. Grand Prixs and Bonnevilles are so similar why are they available with differant motors like that.

The GP went to the S3 with the body style change and that'* around the same time Bonneville dropped the SSEi and S2 supercharged engine. It was rreplaced with the Northstar in the new top of line car, the GXP. The S3 3800 also went to drive by wire TB which is electronic

GP'* got it in 2004. By that time Bonneville was already out of production.