"Power Pack" on the 283 was an option package [different than on a 327], higher compression [I remember it as "around" 9:1] heads with smaller chambers, single 4 bbl and dual exhaust, not specific to vettes, high school bud of mine had a 57 convert with the power pack 283 - nothing special compared to more modern options unless you're trying to build a "numbers matching" show piece .... the casting numbers would say what you have and you'd likely find a lot of discussion on early muscle car forums .... that's a good engine link Tim
