[72freak]

I have three Suburbans...

1999 3/4 ton 4x4 5.7 with 411 or 410 rears (cant remember)...13-16 mpg
1987 1/2 ton 2x4 5.7 with 373 & 700R4.................................15-17 mpg
1972 3/4 ton 2x4 (1989 Suburban 5.7) with 354-ish rear 700R4....15-18 mph

If you want the best fuel economy get a 2 wheel drive, tall narrow tires and try to fingd one with the rear end that matches your driving needs.

Of course.........if fuel economy is a real concern....Buy a Honda