big bolt pattern backing plates

9 1/4's also use only 4 bolts to retain the backing plates but those 4 are the same as 4 of the 5 on the others and you can drill the fifth hole if needed. I have seen five hole backing plates on 4 bolt housings from the factory. The 7 1/4 I mentioned has the fifth hole (bottom hole) already in the backing plate it just doesn't have a bolt in it.

We were talking about the big bolt stuff not small bolt stuff.


Chuck