Hi "Treesurveyor"!
Hope this finds you well!
The MMC switched MCs sometime in June 1993. They moved then to Lockheed brakes, which after a purchase by a mega-international Indian company, became AP Lockheed and then CaparoAP.
They should not be confused with AP-Braking. I have their catalogue up on GoMoG (Brake Section) or merely google them. The assisted brakes they make and supplied are excellent, perfectly proportioned back to front, uncomplicated and not known to fail (assuming all other parts being in good shape). They assist in braking without removing ALL feel like power brakes.
Part#s that I have:Master Cylinder LBBHEL009BP
Vacuum Servo LBDHZC012AP
Brake Fluid Reservoir LB37FF027APThough many Plus 8ers switch to a remote reservoir to prevent the inevitable heating of the brake fluid from the proximity of branch manifolds.
They also sell through a retail network. PREVIOUSLY MMC had LONG used the Girling MC 74066147. [i]
Morgan MCs before 1978 are downright dangerous and should be converted. They have been illegal for new cars for many decades.
BTW, these 1978-1993 Girling brake MCs have a proportioning problem that effects all Morgans using them. Like so many things, the Girling guys adapt to the problem rather than fix it. In a nutshell, their proportioning is 50-50 which is woefully wrong and forces the rear end out in tight corners at even a mild speed. Owners instinctively begin babying their cars in such situations. Sports cars are not supposed to be babied.

The problem can be cured with a smarter MC and excellent tyres. One can also use a proportioning valve.
Be well, fella
L.