I have 3 posi units for the big body Oldsmobiles , #761 posi - 31 spline bolt in retained axles - S spring type , was a 2:73 ratio , . #17-2 28 spline with c-clip style axles , #250 31 spline -c-clip axles - Chevy style clutches , was 3;08 ratio $ 250 plus shipping for any one of these . Prefer to ship in USa only . Located in Hebron Illinois zip 60034

 

Bob,
Can you send me pictures of the first posi listed? ( #761 31 spline bolt in) I am looking for a unit for my 59 full size rear end. Curious about the S spring design. Can you fill me in on that at all?

 

I believe you need the drop out style posi that they used from 1957 to 1962 , this posi came out of a rear load style rear end with the rear cover , years 1970 to 1975 ? BOB