Sorry I didn't see this sooner...
400 heads were all 76 CC chambers, as far as anything I've ever seen. The 493 IS listed as a 400 head, but I would guess it's been milled down for compression. The only REAL difference (from 350 stuff) I've ever noticed were the "steam holes" drilled in the 400s. We've drilled them in many a 350 head for use on 400.
The 2.02 intakes are not "original". The 1.6" exhaust MAY be (I've seen some that were, some that weren't). We see them a lot, where the intakes have been "upgraded" to 2.02. There is no such thing as an "original Torker" on a GM car. Edelbrock intakes are strictly "aftermarket". Or maybe you mean "Torker 1" as in the first design?
8.8-9.0:1 compression is as high as you "dare" for 89 octane. According to my calculations, staic compression with those heads will be right at 9.54:1. Too high, IMO, for anything lower than 93.
Jim