I'm in the middle of putting a 617.951 with a 722.3 trans from a 81 300SD into a 1966 Ford F100 pick up. Have the new front suspension in, set the engine in the frame to make sure there would be no clearance problems, drive shaft, exhaust and motor mount options. Everything looks good, as the 617 is almost the same size as the 6 cylinder I took out.

I got my tires and rims I'm going to use, now it's time to change the rear axle to match the front track width and bolt pattern.

My question is what rpm do I want to be running around 60mph. The truck weighs about 3100 lbs compared to the approx 4000 lb 300sd.

The truck will be a back road cruiser. The land here is mostly flat with a few rolling hills, 55mph speed limits. A few of the main roads are 60 mph speed limit.

I see the 300sd came with a 3.07 gear ratio, but don't think I want to use that ratio to calculate what I want to use this truck for.

Any help will be appreciated. Thanks.