I'm not sure if the seat belt adjustment is stuck, rusted stuck or I'm looking at the wrong item as the adjustment for 1967 122s station wagon.
I've pulled quite hard on both belts as they appear to be connected at some sort of adjustment buckle. The buckle is actually quite thin and would appear to have a very thin diameter roller of some type. Just not sure how to free them up for adjustment. Wetted them with water to see if that would 'lube' them up a bit without using any solvents.
purchased about a year ago, 39K mi. on the odo but lots of rust. Have acquired two brand new fenders-still in bubble wrap and purchase more than 30 years ago. Bought a use hood-better than what was on it for $20. Runs good, lots of body work ahead.
The 1967 did not come with retractable belts, so your adjustment question makes no sense to me. The only adjustment for the stock belt is a sliding portion to take up the slack, which is a pain to loosen to make the belt reach farther.
Klaus If I had a larger garage, I could have more Volvos.