"Something in the Orange"

moparmat2000 said
What's your piston diameter? 2.75" I believe is what the B,E,C, FMJ cars used. Should be the same piston as any M body. If the pistons are 2.60" then it's a 73-76 A body caliper.

This is the post that helped me identify my calipers! Mine are the 2.75” single piston ones.

I pushed the piston in and got good flow back into the master so it seems that the valve was removed when the fronts were updated to disk brakes. I’ll try gasser’s test next. The soft lines look ancient. I’ll keep you posted.