Hope someone can help with this. I have an Auto Ordnance 1927-A1 Thompson carbine (Numrich, not Kahr). I've already made a few improvements, such as installing a new knurled actuator knob, polishing the bolt and feed ramp surfaces, relieving the magazine entry points and re-contouring the furniture in the style of the old '21s (looks terrific if I do say so myself). Can't wait for the ban to expire so I can afford a drum or two

I'd like to further modify the piece to more closely resemble a Model '21/'28. The modifications I'm considering include changing the safety lever to the paddle type, installing a new pivot plate and adding a rocker pivot lever (configured to act as a bolt holdback), installing a Model '21/'28-type stock with slide, etc. I checked the Numrich/Gun Parts Corp. website, but discovered the various parts I need are numbered differently for different models. For example, the pivot plate is apparently different for the '28 as opposed to the M1/M1A1 - likewise the safety and fire control levers. A call to Numrich/GPC did no good - they told me they couldn't tell me anything about parts interchangeability (on their own products no less) and suggested I consult a gunsmith.
The frame used on the 1927-A1 appears to be more similar to the M1/M1A1 frame than anything else. Am I safe in assuming an M1A1 pivot plate will have the same hole spacing/leg length? What about the knurled rocker pivot and safety levers - will the ones specified for the '28 model work?
My shop includes a couple of South Bend Lathes and a Bridgeport mill, so I can handle pretty much anything in the way of machining. All I need is some good advice on what will fit, and a lead or two on where others who have done these modifications found their parts! Of course, if anyone has a few spares lying around ...
Thanks in advance, and thanks for this great forum - I've really learned a lot just reading past posts!