Thanks for the reply! Safety was a concern of mine going into this. I'm questioning how sound 44 year old seatbelt webbing can be. The lack of a shoulder restraint or airbag pretty much makes it a moot point in my opinion, though. Safety is relative, I guess.
I came across that snake-oyl website in my research on this and they seem to be prohibitively expensive. I think I'll try a soak in your woolite idea, followed by a re-dye of the webbing and clean/repaint of the plastics with SEM products. This car isn't Concours material, just a clean cruiser. Thanks for the help!