As a guide, I have the Summit 2801 (close to 068) in my 68 400 Firebird with #16 heads. My car is an auto with factory 3.08 posi. My compression is around 9.6 I would estimate given I used a larger valve relief piston. I like this cam but in my combo it doesn't really come on until about 2400 rpm, or about 45 mph. It would be perfect if I had a little taller rear end and/or a looser converter (like a 2200 or 2400).
In your combo, I agree with Dennis to not go bigger than the 067, or Summit 2800, or another similar aftermarket grind. Don't be afraid of having to go to and adjustable valve train with the 7/16 bbc studs. It is simple and better and opens you up to any cam.
Note: I think the Summit 2800 is on a 110 lsa. Not sure what that does vs a 112 in a low compression motor.
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1968 Firebird 400HO convertible
1971 Trans Am 4-speed, white/blue
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