Gearing and drivetrain experts inside, please.

[JamesJ]

Here are two examples that may or may not help you. On our 65 Corvette I can run about 180 with a 3:55 rear end, 600hp big block 2,800 pounds. On the 63 small block 430hp I can get up to 165 also with a 3:55 rear end before I have to break. We run 225/60/15 which comes out to something like 26 ½ This is at CMS just passed start & finish. Not brave enough to keep it pined going into the turn.
Blue car http://www.hotrodhoodlumstexas.com/I...ace%20(22).JPG
White car http://www.hotrodhoodlumstexas.com/I...ace%20(10).JPG
Both cars have stock trans in them

[USAZR1]

Here are two examples that may or may not help you. On our 65 Corvette I can run about 180 with a 3:55 rear end, 600hp big block 2,800 pounds. On the 63 small block 430hp I can get up to 165 also with a 3:55 rear end before I have to break. We run 225/60/15 which comes out to something like 26 ½ This is at CMS just passed start & finish. Not brave enough to keep it pined going into the turn.
Both cars have stock trans in them

My 90 ZR-1 with 420rwhp LT5 would run 155mph in 4th gear(1:1 ratio)with 26" tall tires and 3.45 rear gear. Rpm at that speed was 7000.
To run 165 or 180mph with either of the above cars would require spinning their engines to around 8000rpm. I'm curious about your engine combos.