My ‘77 front disc squealed so bad it set my teeth on edge. I tried just about every fix. The first thing I tried was that anti squeal brake caliper lube,
It works for a short while, but the squeal comes back, and it makes an un Godly mess of your caliper, I don’t recommend it.
Then I got serious about researching the cause and the cure, ( insert a thank you to 5Twins here ) I started shopping on EBay for two items, circled in red here,
The little silver clips have thin rubber Pads in them that is supposed to help stop vibration, and the larger black shims, also help block vibration. The silver clips I found NOS, the shims were used and rough, but I cleaned them up and used them. They weren’t made to be used together, but they all fit and they don’t interfere with each other so I threw them all in.
For brake pads, I’ve always liked EBC, they’re readily available and work well. And the results? Squeal is gone buddy!