[Bruce Clarkson]

New to the forum. Got my first Pontiac. It's a 68 Bonneville with the 400. Just got it at auction so trying to check everything out prior to putting it on the road.

As part of that, I drained the rear end lube. Had gone to my local parts store and purchased a cover gasket. It had 12 bolt holes whereas I only have 10 bolts. Got on the internet and thought Felpro RDS 55028-1 would fit. Also thought a Motive Gear 3993593 fit. It turned out to be the same fit as the Felpro and neither fit. Although these gaskets have 10 holes, my diff & cover are slightly larger in diameter than these gaskets.

I'm stumped for the moment as to what part to order. Can anyone tell me what to order?

Also, do I perhaps have some odd, non-standard setup? Are there casting numbers or such on the diff that would identify it as appropriate for the car?

Thanks in advance for any help,
Bruce Clarkson