Allows the use of 3905 Transmission in place of 3906... If it worked on FLM chassis why not Gorrilamax? Must have same mounting holes. Cheap solution, I hope...
EDIT: Yes the new 3905/3908 trans is very tough. 2 years of 6s and no problems...
And for diffs. Look into LST XXL complete blue diff on ebay. Very easy to fix into Maxx bulks and very strong See here: