bull.nosed.doit,

I've been out of town and while trying to "catch up", I just read your thread. My 1986 F150 with 4.9L, 4 speed OD [SROD], 3.08 rear gears and original sized tires [215/75 X 15] does as follows in O.D.: 1000 rpm = 35 mph [going downhill]; 1500 rpm = 53 mph; 2000 rpm = 70 mph.

By the way, welcome to the forum!