A500 or 727 with GV?

My 360 is making approximately 370 HP and gets 22 mpg on the hiway with an A833OD tranny, 3.55 gears and a 27" tall rear tire. It turns just a tick over 2000 rpm at 65 mph.

This engine idles almost as smooth as a stocker at 700 rpm and pulls cleanly from 1100 rpm to 6000+. To get my engine over 400 HP would only take a better set of heads than my stock magnum heads.

I drive my car almost daily between Marh and the first salting of the roads in the late fall and the tranny will typically be in the OD 4th gear anytime I am at or above 40 mph. It is not unusual for me to drive it for a number of miles at a time with the rpm in the 1200-1300 rpm range. I have spent a fair amount of time dialing in the carb and the engine does not load or carbon up.

I can't see why you can't build for 400-450 and still be able to run down the hiway in the low 2000's without loading up.