I dont remember enough of the chevelle to be sure. As for the cobra I was talking about your last combo. I agree you should pick up a few tenths before the block splits.
Our cars should be neck and neck in a run, similar weight, "near" identical engine combos and almost identical suspension. I wont know final weight until i'm done with the sound deadener but i figure we'll be within 100lbs. Curb weight on a GT is 3430, I weigh 190lbs and added about 100lbs of "interior" who knows what the seats weigh over stock and the stereo will add quite a bit too. Should be fun, we'll likely be even on HP but you'll have the torque advantage.