Diff questions

[Serum]

i wouldn't use the aluminum cups of flm, since they don't use the large square blocks like the HPI cups now do.

The flm bulkless is more suited for a basher, since they are bullet proof.

a buggy diff won't fit into a savage housing (nicely) because the ringgear is larger of the savage. and to compensate the length, the pinion gear needs to stick out relative far, which causes stress on the bearing, and the other end wont line up with the cup nicely.. (the shaft on the pinions gear is simple too short)

yes, the HB hardened gears will fit. stay away from the kyosho internals, since they are made from cheap/poor quality metal. (the silver/aluminum types)