I bought a MPS from AA about 6 months ago for I was uncertain regarding finding all the right stuff for a rebuilt version, and at that time the AA price was about $50 bucks less I think.
Well I have been driving the car and I am happy with the performance. It idles much better, perhaps run a tad rich, but for my Sunday drives, I say go for it inless you can get a 914 club member to supply you a working one.
If you buy the AA one, it might be rebuilt from my old core for if I recall the core charge was $100 and I sure wanted that money back.