Greenie Question: Gmaxx extended chassis stuff

Not sure wherre else you could get these, be here's the source, they'll have the shafts, looks like about 10 items down the list -

http://www.gorillamaxx.com/gmx07-replacements.html

Don't know about your other questions, I have a G2R and have never tried to fit a body on it (I will, just matter of when...).