I've tinkered with a few 3/4-speed conversions, some of which are still in the fleet and others have been sold off:

A 1948 Claud Butler, which came to me with its original rear flip-flop hub and 597mm/EA1 wheels. It now has a Sturmey Archer FM rear hub built into a 700c rim:



1971 Raleigh Competition w/ a rear S-A AW hub:


I've found that early 70s Raleigh Super Course makes a good candidate, and I've done a bunch of conversions with 3-speed hubs:

This one has an S-A AM rear hub built into a 27" rim:


Different frame but w/ an AW hub, 700c wheels, upright bars:


This one got a fully respray w/ matching fenders:


This one's a Raleigh Int'l converted w/ a S-A FW hub and 700c wheels:


And here's an 80s Dawes Galaxy w/ a rear AW hub:


Neal