need a half second

If you are only running the Comp 268H High Energy cam, I'd say more cam is in order (I run that cam in my 3/4 ton 4X4 trailer towing pickup). An XE274 would sure perk it up above 3000 RPM. The Performer RPM intake will also help, if for no other reason than taking 40+ pounds off the nose. Beyond that, a 600 is gonna be slightly small, but good for the street. Play with an open hole spacer at the track. Some mufflers can be restrictive too, even if "flow" is part of the name.

You didn't mention the converter, actual compression (I'm guessing about 9:1 unless those heads were really shaved), or what your car weighs. I would think with the above cam and 3.55 gears, a converter with a 2800-3200 RPM stall speed would help you out.

Beyond that, make it lighter.