Did you get it figured out? The 2wd seems to be different from 4wd. It looks like same unit for late 63-68 Chevy 1/2T/3/4T 4wd....and GMC 1/2T 1966, 3/4T 66-68 4wd. Non verified info but pretty close.
Lares 8669..very expensive.
or this (unless that is an old price or old availability). You could also find a donor unit/rebuild yours.
Sorry it took so long for an answer.
Looks like he is on ebay,
Free Ship