build a gmaxx and i need help

[suicideneil]

Dont use the Pro diffs, they will lower your gearing too much, meaning you need a tiny spur and/or a huge pinion. Hotbodies lightning buggy diffs work fine, and should be easy to find, if not look for ofna buggy diffs.

18/68 does sound a bit low for 4s lipo, probably about right for 6s maybe (aiming for ~40mph).

To make the UE suspension arms fit the FLM bulkheads, you just need to shave a little material from the arms where the hinge pins go, as they are a little wide for the mounting points on the bulkheads- only a mm or so from each side, nothing major or difficult to do.