[wallot]

diff cups and internals are the same so you can put on whatever ring gear you wish.

6T and 5T may look same but they are different. They are cut differently. so you always need to match gear and pinion. however you can slap 6t gear onto 5T diff cup
6T and 6 also use different internal big gears - for 2.2mm pin compared to 2mm in 5)

never had any issue with mugen diffs. they just need to be shimmed properly and once in a while play in the bulkhead checked - I am going to replace bulkheads before coming season and the truck has about 20 races.