I have seen different styles of mountine options for center support bearings.
Some are the same width as the tamiya frame others are skinny and will need to be bolted to a plate and the plate bolted to the frame.
Rc4wd has a few styles that I have used with good results. They now have a nice skinny one that looks like it bolts to the frame.
http://store.rc4wd.com/Transfer-Case_c_24.html