I told you how to check it. The spec given by mopar was for the Bendix booster with a Bendix MC attached. Regardless, the key is that the piston seal sit rearward of the compensation port by .010-.020". When brakes off this allows line pressure to bleed back into the reservoir. Those aftermarket versions do work. Though the ports on two sides does not give a good appearance to me. It is a shame the manufactures went that way to make it a universal fit.

When you hold the MC you can press the piston in flush and look at the compensation ports. You would see the piston minor dia. Press more and the black seal should cover the port. The piston rod in booster set the piston to the proper setting.

I do have Casting # 2225621 Bendix 67-69 Hemi MC core. It has been sleeved with stainless, and I had it as a backup. It just needs to be assembled with a kit. If you are interested, you can PM me.