K10 wheel hop when braking?

[topside]

Noticed something new on the '79 K10 I recently purchased: when slowing down from about 50MPH or more, the right rear wheel & tire start hopping up & down. It can be modulated with the brakes (harder = more hop). Pretty weird. I'm thinking shock absorber as it seems to stop straight. Brakes were done last year & there are no visible fluid leaks, but the shocks are old. Leaf springs look OK. Having weight in the bed minimizes it somewhat. I bought the truck from a friend, have driven it before, & know the very good mechanic who did the brakes.
Whaddya think? Thanks in advance...

[76 k10]

thats werid. id try to get new shocks. and check your u bolts

[topside]

UPDATE - maybe...I checked the master cylinder and noticed that the front reservoir (the larger one) was down about 3/8" on fluid; I'll have to see if that's for the front or rear brakes. Bolts tight, leaf spring OK, shocks look ancient but were working fine a week ago and aren't leaking. I'm starting to think the R/R wheel cylinder has seeped fluid onto the brake shoes...

[VileZambonie]

Pull the drums and inspect. Take pix