You're a shoe-in for Craigslist. You've stated you like retro, prefer downtube shifters and need a larger frame. Most every company back in the 80's offered road bikes with frames up to 27" (68.5cm) made of chromoly steel, with of course, DT shifters or earlier 10 speeds with stem shifters.

Just search for "tall bike" or "tall rider" and see what pops up.