Two center hole sizes for that cast iron bell housing exist, the SM420 is a smaller hole than say the SM465. One is under 5'' dia. the other is over 5''. L6 fits V8's

Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
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