1964 Valiant 4 Speed with Posi .

My 1964 Valiant has the Factory 4 speed and Posi Rear end . The rear wheels have side to side play . And will eventually lock up .
The wheels will not want to turn . May be just the axle bearings . But I am not the expert on this .

My question is how to identify the differential . For 1964 . Chrysler had 2 Posi Read ends . I believe mine to be the smaller
one . Which I do not think parts are available for . My Posi has a more flat rear , removable plate on it . And no tag.
Is there any sort of spotter's guide to tell the difference between the two ? My 66 Formula S Had a 833 and a Posi .
I believe the Posi had a more rounded . Removeable rear plate .

I found a 1964 Dart with a 273 and a 833 in it . If the Rear end is the rebuildable Posi . I would buy it . And use or rebuild .

Any advice appreciated