Thanks Jeff:
Unfortunately I may need to wait a while before a 71 Suburban shows up on Craigslist, and the good riding weather is tempting me to get a bike right away.
I found a blog post by a fellow who converted a Raleigh Sprite to a 3 speed Sturmey Archer, but I don't think he will part with it...
I'm guessing that the late seventies would be the timeframe for me to look at. Ten speeds were wildly popular then, but the 3 speeds were still around, and the 27 inch wheels had become common. A childhood friend had a Huffy 3 speed back in 1971 or so that was the envy of the rest of us. I think it may have been a rebadged Raleigh or Phillips.