Thanks for the help. I gave both of the ideas you had linc a try to see how the would work. They both turned out good. One has a advantage over the other due to size of the dst shaft is 5mm though. I also took some time and got the plastic spur from kyosho to work on the crt .5 center differential. I use it in my ls10 so it will work in really any of the 1/10th scales that use a center differential. I will be putting together a write up on the mods needed for it. Now I need to finda new center cup for the crt .5 The manual doesn't list a part number an I can't find one on a-main. Maybe it is the same as the front/rear differential cup. They are just keeping it secret from me. You got a UPS box on the way to you. Got it out of here a few days ago.
Here's what I've come up with. The mod to the existing cap and spur will work the best due to the 1/8th spur has a center hole of 6mm and the shaft on the axle drive is 5mm.