I run a 270 with a 3.08 axle in my '57 GMC;my engine is a little worn out though,and that coupled with LT235/85R-16's means it doesn't take too much of a grade to slow it down from my 70 mph @ 2,300 rpm.(It has a knock at anything over 2,500,so 2,300's cruise redline for it.)
Speed


1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck