2.76s weren't an axle package, just an OPTIONAL ratio.

Superbirds with automatics had 3.55s & 8-3/4" ONLY
Superbirds with 4-speeds had 3.54s & DANA 60s ONLY

I'd "assume" someone could've put in 2.76s in an attempt for gas mileage.

Quote:

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Did the 22" and 26" use the same size
cut-out in the core support?

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I think the 4" difference in the core support is all to the passenger side.