Auto Parts: distributor shaft sizes, ford 351c, distributor shaft

Question
i am in Australia, hope info i give will be applicable to answer from America. i am building a 351 CLEVELAND V8. later model, which ran smaller dia. shaft on distributor. as opposed to early models which ran larger dia. i intend to fit new MSD distributor. it will not fit because it has large dia. shaft. a machinist will turn it down. but to what size? i could take the original BOSCH to machine shop and instruct to turn down to that shaft size, but it may be worn through years of use, therefore will not be correct. i have this info. relayed to me. MSD has shaft dia. of .531 inches. ( 13.50mm ) most Fords run a .531 inch. 1968- 95 Ford 351C had a .490 inch. and lot of GM have .491 inch.(12.50mm) probably the only people who know the EXACT size to turn this down to would be BOSCH. being as how they made the original units, but i am unsure as to how to get their specifications. hoping you may know or are able to steer me in right direction toward precise dia measurement of distributor shaft to suit later model 351C . thank you, hope to hear. Lee.  7

Answer
    This is a problem.  Here in the states all of the shafts are the same size.  The difference between the 351C and the 351W is the diameter of the gear.  All American Fords use distributors made by Ford themselves.  I know that there is some interchangeability between Australian 351C and the American version, but it is mostly the big parts.  The little stuff is mostly completely different.  The important thing for shaft size is that it is compatible with the oil pump driveshaft, and that the correct gear fit onto it.  So, the important thing is to make sure you have the right size gear.  Buying the gear from MSD might eliminate the shaft size problem.  I don't know if there are two different size oil pump driveshafts; in the U.S. there are only differences in length.  Have you tried talking to MSD about the problem?  I don't know how much support they offer to the Aussie market, but they are very friendly and helpful folks.  You might also get some help from Mallory, Accel, or one of the cam companies.