Friend of mine and his dad built a 79ish grand prix back in the late 90's with a 403, 2004r, and 2.14 rear and he said it did upper 20's.
My turbo 3.8 drawthrough cutlass with 3.42 and 2004r and gets 22-23 at 73mph ish average. Its still a carb though.
Getting to 30 is tough.
It would HAVE to be efi, and probably 4 or 6cyl manual.
I think a 3800 V6, t5, and 2.41's or less could do it. Some 205 or so skinny tires, and gingerly driving might do it. Problem there is a 3800 is all cast iron and pretty heavy.
For the unlimited budget option a direct injected new 4.3 (basically the lt1 series 5.3/6.2 but v6) with a t5/t56 (maybe even the 8 speed auto or whatever) would do it. New trans programming is so efficient that it might not be that beneficial with a manual. That setup should do it. They get 22 in a truck that weighs 5000+lbs so a 3000lb g body with much smaller area and some tuning, strategic removal of governmental emisions controls and stuff would help.
Other option is an ecotec but they had a specific bellhousing and the only trans that works is out of a solstice/sky for RWD.
Other option would be an atlas series I4/I5 out of a colorado.
