You are right that even my 62 will come in a little small for a traditional fit. the 62 is really intended for a saddle height up to about 82-83. For a frame a reference, here is my current main ride:
Frame bag No.1 by
rperks1, on Flickr
the saddle height is about 80cm in this picture. My upcoming model will have a lower bottom bracket than the Roadeo shown. Combine that with the center to center seat tube measurements I am using and a 64 could probably work out pretty well for you. I have only had a little interest in that size, but enough that I am still keeping it in the line-up.
It sounds like the easily available vintage steel may also be a bit of a problem for your fit, as the older bikes tended to have shorter top tubes. Keep your eyes open for a used Fuji America, s-12s or LTD, these will pop up from time to time, the sizing will be close on the largest sizes (64). The models around the 1980 year give or take a couple of years are a decent low cost way to try out a bike with a low-trail front loaded bias type of bike. Most of these can easily be converted to 70c as well.
Good luck on your search, the journey is part of the fun.