'66 and earlier Volvos had 10 splined Dana 27 rear ends. Posi units can sometimes be found for those. I have one which I will probably put on e-Bay sometime soon.

'67 - '69 Volvos with drum brakes (120s & 1800s) had 10 splined Dana 30s which were peculiar to Volvo. LSDs were available as an option on those cars so they do exist but are very rare. Unfortunately, you cannot use a LSD from a 10 spline Dana 27 in a 10 splined Dana 30 diff.

From '70 on Volvo used 27 spline Dana 30s or the 1800s, 140s and 240s, although some 240s had the Dana 1031 which is a variant of the Dana 30.

LSDs are quite common for those diffs as Jeep used Dana 30s in a lot of their front axles. I have one of those too, which I'm thinking about putting up for auction on e-Bay.

If you really want Posi on a '67 -'69 1800 or 122 it's probably easiest to buy a disc braked Dana 30 rear end out of a '70-'73 1800 and put a 27 spline Dana 30 Posi or Detroit TrueTrac in it. Then you'll have 4 wheel disc brakes & posi.

Roj

'67 1800 S & various other Volvos