m4 boneyard stuff

so now i know this is final. i got a echo1/jg m4 comando and i got it from the boneyard so i might have to fix it but i don't know yet since i haven't got it but my question is if i could interchange parts from my stubby jg m4 into it if it need be and if not i'll change the front wiring and handgaurd stuff and stock to the stubby but that might be alot more work. just wanted to know if i could interchange parts.

by the way this is what i bought http://www.airsoftpost.com/bone-yard-echo1-m733-airsoft-metal-gearbox-p-31289.html and now it's proccesing

besides a metal body and hop up what else should i change as well?