Low Speed Brake Shudder - Thoughts?

69 Barracuda, Kelsey Hayes front disc, drum rear - power brakes.. I'll start by saying this is not a rotor warp. I'm very familiar with that. This is a shudder that is in the final 10 feet, 2mph, of a stop. It's in the front, I'm thinking a loose caliper? I am also getting a medium warble sound out of the rear drums, not a squeal. Everything happens at once. Everything is fairly new 2000 miles on them.
Any ideas? Before I go exploring. Thanks