Hey there, I know this is an old post, but I ran across it while looking for some other information. I have a 1973 Century Resorter inboard with a 440 Chrysler in it and it still had the OEM distributor with points, condenser, ballast resistor.....etc. Even after new condenser, ballast resistor, and points and setting the dwell by the book - the boat still started VERY HARD every time and would periodically shut down after running for a few minutes. Installing new parts and tweaking seemed to be a yearly ritual that I was ready to part with. A friend put me in touch with an E-Bay "all-in-one" electronic distributor with the built in electronic "Brain Box". The price was like $128 I think - clearly a Chinese knock-off. I purchased it and it appeared to be very well made. I ran into the same problem here with the short shaft. Through forums such as this, I quickly understood my dilemma.
I initially thought about making a longer shaft and installing it but I could not remove the shaft from the reluctor assembly on the head - it is all potted together rather nicely and rather permanently. So, I took an even easier route and just made my shaft longer. The shaft is 1/2" so I used a short stub of 1/2" drill rod to make my adapter. I had my machinist at work make a small adapter that just lengthened the distributor shaft the exact amount needed. I affixed it to the end with a roll pin and ground both sides of the shaft flush. There is no way for the roll pin to come out because of the sleeve it is in, and I made the fit a "line fit" - size for size. The finished product looks amazing, installed effortlessly, and the boat starts like a dream and runs even better.
This is my very first post, so I'm not totally up on how to post photos and such, but I do have photos of the adapter, a sketch of the adapter I had made with dimensions, and photos of the finished product (assembly) I'd be willing to share with any.
Had I known this was such a common problem, I would have made a few extra adapters at the time and just shared them with anyone else in the same situation for postage and a "thank you".
Great forum guys. -BiLLy