The Best to use is PMI, they have worked the best for me i use the SL kit with double seals and metal scrapers the blocks are fully sealed and work well in dirty environments I also use oil instead of grease helps prevent plasma BB's from building up around the blocks, If you use them in an exposed to weather situation keep them sprayed with phosphate type lube like royal purple Max film. as for gear boxes i keep them all the same if something goes wrong (and it will) it make diagnostics easier and you can swap motors around for testing