[RichardJ]

The MC for manual brakes have a deep hole for the brake rod. The MC for power brakes have a shallow hole to mate with the adjustable pin in the front of the booster.
CPP sells universal MC's with a plug that drops in so it can be used for manual or with a booster. I've made plugs like that from aluminum rod. Bull nose one end and drill a shallow dimple on the other end so the booster pin can't wonder off center. CPP adds an O-ring, but there is no need.
The important thing is that you measure the booster pin and the MC hole depth accurately. This is important even if you get a power MC.
They have a tool for this measurement, but with care can be checked with basic measurement tools.