all the parts are interchangable. I use to run a 8.5 pro and had an rtr for a cheap emergency spare parts car. The differences are the following, maybe i wont leave anything out:
Pro has:
7075 machined chassis
7075 machined shock towers
7075 braces - front, center under center diff, and rear
7075 motor mounts
carbon fiber radio tray and brake/diff brace
adjustable turnbuckles
spider center diff
aluminum wing mount tubes
capped wheel nuts
cnc machined front knuckles
ball bearing supported steering bellcrank
aluminum servo horn
I am sure i forgot some things, those are the main things though, but look on ebay, there are still people ebay'n pro kit part outs, can get all the good parts for pretty cheap, I bought alot that way!!