Personnally I think the Mikuni's are easier to tune. Send the carb to jerry and get it bored to 41.5. How does the slide look in the mikuni on both side's? What Style mikuni 87 or 88-90 style. Your jetting will be different. with your setup and the 88-90 carb I'd say start about 420 and work down. My 89 w/ stock ports and carb, V2 reeds and a Q pipe likes a 390 at 75-80 degrees about 600 ft above sea level. Same combo with fmf liked a 380.