project 39,

If you buy a rebuilt or new alternator from your auto parts store, it will have the proper diameter pulley on it for its intended application. The same would hold true for a salvage yard..the alternator will have the pulley on it that makes it work right.

The RPM range of your 235 won't be far enough out from alternator equipped engines for you to need to change pulleys. It will probably charge fine. The single wire alternators require an initial 'rev' to get them going, but this would be done almost automatically and is the nature of this style.

Your '39 probably has a big old belt on it and this might be the issue. I am winging most of this post, so the best thing for you to do is go to the 'search' icon in the upper right of this page and look for 'alternator pulley' or 'generator pulley' and read the true poop!

Stuart