I have had MT 1 Redline in there for about 5 years,,,but not many miles on it.
Slow secros on 1-2 are just something this trans has. Some must of been worse than mine because they had a kit for the 90-91. Slow syncros are a small price to pay having for this very H. D. trans.
I've used Stalube 80 with a little LSD juice, it worked good.
Used synchro too.
Down side to Redline is it seems to evntually eat silicone used on for trans gaskets, IMHO.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.