I don't know a lot about the plain bearing Magnum engine designations, but I know that the early ones for Hobby Shack (now Hobby People) were made in Taiwan and very close to being a duplicate of the OS .40FP. Apparently, Hobby Shack/People took the production to China at some point and had a new engine designed. The Taiwan facility became Thunder Tiger. It seems to me that there was a GP.40 in the TT lineup, and it was pretty much the same as the original Magnum except for badging. If you'd look over your engine and see if it says "Taiwan" or "China", I would feel more comfy offering ideas...but contacting Randy Smith directly via email or PM would probably be a fine idea, especially if you give him that info. He might be able to fix you up with the prop driver, or know what else will fit (maybe .40/.46LA?), and most certainly can provide a venturi and the best NV Assy. in existance.  Steve