I own a cross breed, it is a '68 F-100 custom body on a '78 F-150 Ranger 4x4 Chassis, I used the 390 and the C-6 tranny housing from the '68, then used the '78 tranny guts and transfer case. I think it has 3.00 gears in the rear and 4.10 in the front (not good, I know). My speed-o-meter is registering 25 at 50-55mph. I have a green gear and 33x12.50 15 tires, can anyone help me figure this out? I am about to put the '68 rear end in it and see if that helps, its possibly a 4.10.