Cutting up a rear axle.

I have a a body housing. I was going to use a sure grip clutch center ot of a truck. Th splines on the axles from the truck are the same as a 8 3/4. The truck axle fits the 8 3/4 center . I can provide pis if needed . The total lenght of my DC a-body dana housing is 55. The pads are 43 center to center. I asked the guy I got the housing from and he said the dana car axles are alot larger 35 spline. Whats up with That? Can I use two different length 8 3/4 axles from Moser with this center from the truck. Or should I get the larger gears for the center.? Anyone run into this?