The photo didn't work in my browser. But you mentioned drum brakes. The last Volvos to have drum rear brakes were the P1800,122S and the PV544. So it's probably a rear from one of these cars. They actually used USA built Spicer differentials so you shouldn't have any problem with parts. Also the Volvo brake parts are available but I have heard that the racers modify it to take Ford rear axles and drums. Did the brake drum remove with a puller and was on
a tapered shaft with a key? If so this is most likely a Volvo rear from one of the aforementioned cars. These model Volvos are the only cars I know of that used this type of rear drum mounting. Grassroots Motorsports has restored a
beatiful 122S and you can check out their site for info on the brake conversion.
I believe they were going to do something to modify the 122S for better rear
brakes. Just do a web search for Grassroots Motorsports. I don't know the URL.

Dave 82 242ti 276k mi.