Thanks for the input guys.
Pretty sure 66fleetside is onto something here. The GM truck 12 bolt has been around since 63, but the 63-64 were the "old-style" 12 bolt with 17 spline axles and different trac bar mounting locations than 65-later.
Called National Seal this morning and found that the repair bearing Wrenchbender had told me about some time ago should work for my application. That bearing number is RP-6408. The oil seal is 8477S.
Seth you have mail.
