Here's a few places for oil for engines and transmissions, delivered to your door...

Redline shockproof heavy (Transmissions) and other redline products... HERE

Mobil 1 V Twin engine oil (engine) / Trans lube 75/90 (trans) and other mobil products... HERE

Good old HD primary oil works best for me in the primary, gives a better feel to the clutch than the synthetics do.

Also see here for the SYN 3 in the transmission... https://www.hdforums.com/m_273708/tm.htm