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Cummins 4BT 3.9l four cylinder turbo diesel is an absolute natural. It's a little scimpy in the hp department at 120 but makes gobs of torque, is extremely fuel efficient, and weighs only about 100 pounds more than a 460. Find an old bread/Frito Lay/FedEx truck with this engine and a T18 or T19 transmission behind it and it is a relatively easy swap. Am in the process of doing this same swap in a 73 F100 and it nearly bolts in. Lack of overdrive in the F100 transmission was the biggest drawback but am currently experimenting with a later model 4sp OD. If you've got 35" or taller tires, direct drive high gear might not be that bad of a problem with the 4BT's 2500 rpm governor speed.
Axle should be fine, the Ford 9" is a near perfect balance of strength, light weight and compactness and has been a high performance mainstay in everything from drag racing to prerunners for decades. Long after the "flavor of the month" or expensive hybrid and fabbed axles have lost their luster, the humble 9" will still be handling all of the abuse that a heavy right foot can dish out.
Axle should be fine, the Ford 9" is a near perfect balance of strength, light weight and compactness and has been a high performance mainstay in everything from drag racing to prerunners for decades. Long after the "flavor of the month" or expensive hybrid and fabbed axles have lost their luster, the humble 9" will still be handling all of the abuse that a heavy right foot can dish out.
Its a nice axle for sure but its the basic design that has made it popular in drag racing. The formula for building one that lives under the most severe abuse is to replace every component made by Ford.