Ed, Looks like The Filling Station and Jim Carter's Truck are both in a back-order status. Chevs of the 40's has the 3.55:1 Ring Pinion Set, a bit less than the other two vendor's regular prices. I've not used this ring/pinion set from Chevs, but other parts I've sourced through Chev's have been fine, FWIW.

Doug

1947 2nd-Series GMC FC152 3/4-ton
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1953 Chevy Bel Air Sport Coupe Powerglide