How toDetermining what year Diff I have and gear ratio?

[332fly]

Gentlemen, I recently got a 33 sedan with front and rear vette sus, trying to figure out what year and ratio I have, I found these #’s on rear cover 14078878 and 41254 looks like 12” Rotors any help would be greatly appreciated. Thanks,Vann

 

[vetteoz]

Can't see in your pic , at top center ,is there a bolt that connects the batwing to the diff head ?
Refer pic below , D44 shown on top
If so it is a D36 , std auto diff .
If not it is a D44 ;the manual trans only HD option.
Year range is identified by brake park brake arrangement. 84-87 have drum type internal park brake .
88-96 have PB as part of the caliper

On the underside of the diff head should be stamped numbers indicating ratio and production year