I bought a set of M Calipers from Bruce Stone and had them rebuilt by Eric the brakeman Shea. Now I have decided to go another way for my front brakes.
These were installed, bled and are perfect.

$349.00 + Shipping you get the new pads and speed bleeders for free!

You can use these on early cars with your solid rotors by removing the spacer between the caliper halves. You can use these on late cars with a simple bolt up. You can use SC vented rotors if you really want to make a cooling improvement.

PM SENT

Alex,
Apparently the difference is if it is an early car, you need to remove the spacer between the caliper halves. If late you are good to bolt up and go.
The transition is 72.8 or there abouts. Dual bleeders are early, single bleeders are late.