OK, so ideally there should be a clearance between me and the top tube, but it's not a deal breaker (monetarily and health-wise). I'll pay attention to the top and head tubes when I go check out used bikes. I found a Trek 1000 for 250 off CL. The seller doesn't seem to know the size, but I'm checking it out tomorrow.

Do you think it will be worth checking out a 60cm-sized road bike? It sounds like what you're saying implies that top and head tube sizes aren't fixed with the bike "size" given in centimeters. So a 60cm-bike might sound too big for me, but it might actually have the right top and head tubes I need?