Easy way to tell is remove lower cover. 5-7/8" between pressure plate bolt holes shown here is for 10.5" clutch and approximately 5-1/4 between holes is a 9-1/4 or 10". Even easier is that 10.5" uses 3/8" pressure plate bolts (9/16" wrench) and 9-1/4 and 10 use 1/2" or smaller wrench.