I am considering picking up a used early 2000s Lemond Buenos Aires. Frame is 53. My current bike is a 54. Current bike is a semi compact modern frame with 545mm effective top tube. I've found that 545mm eff tt is my limit on the small end and 545-555 is my sweet spot from other bikes I've owned and rode.
The person selling the frame says his measurement center seat post to center of head tube is 550mm. To me that sounds like it will fit me but I was looking at the Lemond mechanic's guide guide I found online doesn't list the eff top tube but it says a 53 is good for rider around 68 inches/5'8". I'm 5'10". Do you think the 53 would be way too small for me? I've read something about how seat post angles and stuff on the Lemond make the eff top tube measurements misleading?