I just went through this problem. This is the answer I got. If you have a stock 340/360 it is not a problem. If you are going to be pushing anymore hp than that then go the aftermarket axel route. To get your axels and drums properly drilled is going to cost you a minimum of $175 after shipping them.
Get in touch with Outrageously Vintage (they are a sponser on this site). Bob and Cici will be able to help you out.
I just bought a set of axels and green bearings from them. The price was right and the service was great. They included everything you need including gaskets and most importantly, good advice.
Jack