KURT,
is yours a miata or the B6???...some say the B6 small manifold has the improved crank with the bigger crank nose...i haven't seen it yet so i can't confirm...however according to your article only the 91 models onwards has that crank but B6 last production was in 89/90 after which was the BPT...but i am replacing mine with a miata crankshaft which has a bigger diameter crank nose...not sure what year coz it came in an engine kosong...hope it works