mdross1,
I have two 385-powered cars - very similar in specifications but not in appearance. My Cobra has a 521 EFI, C6 and a 2.88 Jag diff. With 46% front, 54% rear and 3200 lbs all-up weight it can spin NT05s at 100mph if I whack it. Needless to say I don't. It gets around 10-11mpg if I am conservative. It just crossed 31K street and track miles.
The other car is a 1981 Zephyr (Fairmont badge twin) wagon with a 557, a 950 Holley, C6 and a 2.73 '04 Cobra IRS. Its weight is close to the Cobra. Its performance is similar. It has done about 8K miles on the street (need to put the diff cooler in before tracking it) and can get 14mpg at a steady 65mph.
If I could get a 4-speed automatic with an overdrive the highway mileage would be better no doubt, but it's hard to find one that will survive track use like the C6s, now that I know Carl Rossler knows how to build them for that.
Grin city every time I take one out, which is nearly daily...
Tom
PS: Here's one:
and here's the other:
