The center diff that comes with the GST is extremely hard to turn around without the transmission. It's like you can barely turn it around by hand, for some reason.

I'm going to order the e-maxx input shaft and revo slipper and just run it like that. If the tranny breaks, I'll either try to install the flux tranny in the GST or use the standard GST center diff with some sort of mounting system. Waiting to hear back from GCM.