The axle in a C70 would probably be an 18,500 Eaton. You will almost need to keep the 2 speed behind the 5 speed, and I don't think you will find a better ratio than what your truck was born with. It was probably a 5.29/7.20 or a 4.86/6.86. It depends on which 5 speed you have. If you have a close ratio 4th and 5th, it will have the wide ratio Eaton. If you have a wider ratio 4th and 5th, you will have the closer ratio 2 speed. You will need at least 10 speeds for the little 4-53T and a 5 and 2 is the most practical way to get 10 speeds. The frame width of your 1 1/2 to n should be the same as the C70. I
