I put an 8-3/4 in my 70 challenger. I bought the axles, pumpkin, and housing separate. I put it together and the axles are sliding about a quarter inch in and out. How do you put it together correctly?? I think I messed up....

If its a SG you need the buttons one on each end of the pig where the axle ends are and the roll pin that holds em together. If needed to check by removing the axles, pull the axle almost all the way out till the splines are still on the inside of the seal then wrap some brown grocery sack paper around the axle on the outside of the seal tight then slide the axle/paper in till most of the paper is in past the seal then grab the edge of the paper & relax it a bit & pull the axle out holding the paper in place so the paper protects the seal from the splines. Reverse that for the install. You did use the white foam and the steel shim gasket on either side of the b plate correct? And the threaded adjuster is there & accounted for (ideally on pass side axle)

I will look into that...thank you!

Holler how it progresses/what you find

Only a clutch style uses the buttons and roll pin. The cone type does not use that button