Hold it, are these for refurbished original parts or high quality reproductions? I know MBZ still makes certain parts for classics, but in this case it would be a third party with licensing rights, according to you. The closest 'clean' MGA I came across was in sterling blue with light cream interior. I wasn't too keen on driving an Easter egg.
There are crap tons of new production parts available, although as I said of varying quality. You can more or less build an MGB out of a catalog. British Motor Heritage still stamps complete body shells from the original tooling.
Since the company that made the cars is more or less defunct, there are no remaining "authorized" repair parts but the industry still thrives. A lot of the OEM suppliers are still around, although Lucas parts now are hit or miss. SU still makes new fuel pumps and carburetors, along with VERY high quality repair parts for their old ones.
And, as an example of the cottage industry stuff, I'll mention axle rebound straps. The A and B both have virtually identical rear suspension that's fairly antiquated by today's standards(although none the less works well on these little lightweight cars). They have a live axle suspended by a leaf spring at each end and an Armstrong lever action shock dampen motion. In all of this assembly, there is what was originally a rubberized cloth strap that attached between the axle and the body on each side to limit the maximum downward motion. Mine were still serviceable-although showing their age-when I replaced them at 45 years old as part of a complete rear suspension rebuild. I've been widely advised that the new ones from Moss aren't very good, but for $30 a set a guy out in California makes some from parachute grade nylon(that's as compared to $20/set from Moss).
And, again, for something that's not available new, chances are someone rebuilds old ones.
Just earlier this week, I bought a brand new, in box Lucas 25D4 distributor. The construction isn't as good as my original, but the car runs a LOT better with it than with my old sloppy one. I'm sending the old one to Jeff Schlemmer for a rebuild and recurve and will swap it back in when I get it back(probably in 3-4 months).
Probably the only things not available "off the shelf" are new production engines, transmissions, and other major drive train components. At the same time, the B-series engine(used in both the A and the B, although with different displacements in the two cars) was a mainstay for BMC and later British Leyland so there are TONS of them around along with most anything you would need to make a solid block functional. They're a pretty bullet proof engine anyway. Although they don't turn out huge horsepower numbers, they have a fairly long stroke which makes them very torquey. The only real weakness in the design is the "siamese" exhaust ports(one port for 1 and 2, one port for 3 and 4) restricts flow somewhat. The design also makes the Cylinder #3 exhaust valve(valve #6) run fairly hot and it's prone to erosion if the engine is run lean for too long. Aside from that, though, they just keep ticking away and will often even seemingly run fine even with serious problems. You will need to pop the valve cover every couple thousand miles and adjust valve lash, but that's a 10 minute job after you've done it a few times.
And, all that aside, I like to keep mine original but do make some concessions to modern technology. The earlier Bs(and I think As also) had a pair of 6 volt batteries in series. Most everyone now runs a single 12V battery that nicely fits in one of the battery boxes-these are lighter than the dual batteries, more available, have fewer connections to cause problems, and simply are better batteries. Electronic hall effect sensors are available to replace the often problematic points in SU fuel pumps, both as a bolt-on for existing pumps and as a complete pump. My car came with an aftermarket electronic pump that worked fine and is pretty readily available, and I still carry that pump in just in case(the biggest fault of most of the aftermarket pumps is that they run all the time and make one heck of a racket). I reluctantly installed a Pertronix electronic ignition-actually prefitted to the distributor I mentioned above-primarily because ignition points are a bit hit or miss in quality.
Although mine is driveable(I drove it ~60 miles home right after buying it) it has turned into a bit of a rolling restoration as I tackle small jobs along the way. Probably the biggest was the rear suspension rebuild necessitated by a broken spring, which consisted of two new leaf springs, all new rubber bushings/pads, new rebound straps, and all new hardware. I've put a new(factory style) exhaust on, and most recently rebuilt the steering. I have the clutch hydraulics, a cooling system flush/rebuild, and a four wheel brake job(including hydraulics) to do.
I do virtually all the work myself, and rarely need more than a floor jack, a couple of jackstands, and a basic set of hand tools(sockets and wrenches) to do a repair. About 80% of electrical diagnostics can be done with nothing more than a 12V test light(which you can make yourself if you're really cheap) and the rest just need a basic VOM to get everything done although a true automotive meter helps. I also have a timing light that gets a decent amount of use, but many folks get by fine doing nothing more than static timing(which is done with a 12V test lamp) and road tuning. After rebuilding the steering, I set the front end alignment in my garage with a piece of string, a couple of wrenches, a set of vice grips, and a few trips around the block to test adjustments.
