Tom,
I have the same set up as you, except for a 5 spd. Seems to me that tranny types souldn't matter, but I could be wrong.
Anyway, after a few failed attempts at speed gears, I wound up with a 40 tooth speedo gear. Speedo registers 61 mph while I actually do 60 mph....close enough for me. A 41 tooth may put me dead on, but I'm too cheapo to buy yet another speedo gear...
Ivan