Great write up! This is my first post. I jus bought this same buggy and the 670 was exactly what I wanted to run as well while keeping fnr. I've been searching like crazy trying to find a chain driven fnr gear box and I found on but it doesn't look like it will except our cv axles and idk what ones it used. But after seeing what you did I think that's the route I want to go also.
Sooo... do you think you could go into greater detail as to what you did to modify the gear box to work? Pix if possible? I would greatly appreciate it. The only other option I've seen is this and I'd have to run diff axles and prob diff hubs and it jus seems to be a pain haha.
https://www.ebay.com/itm/930-CV-LIVE-AX ... %7Ciid%3A1