Here you go... I did this on my 60 235. It takes some "shadetree mechanicing". If you take a forged big block or small block short water pump crank pulley you will find the inside circle fits perfectly inside the 235 pulley so that it is indexed. Next you have to rotate it so that you can drill 3 holes without hitting one of the rivets, you will actually nick a couple of the heads but no big deal.
Use the proper diameter center punch to get exactly in the middle of the hole then drill them out. Tap the holes from the back to front and you have a single or dual accessory crank pulley. I have some pics if you send me your email.
Phil