MASTER CYLINDER

I think the wire retainers came on board in 1970.Or with the KH brakes.
I think the screw-tops are drum/drum only?With equal sized reservoirs.
I'm kindof guessing.
As long as the bore and reservoir size works for you, I wouldn't worry about the cap style.
I prefer the capseals with bellows; no venting required.
Brake fluid loves moisture. It will suck it out of the air like a tree sucks it out of the ground.But the brake system hates water.