Originally Posted by
roccobike
Depends on how "exact" you want to be. I would say you could make a 54.5 work if you are willing to mess around with different stems and/or consider zero set back seat posts. If your attitude is I'll make it fit, then yes I think it will work and it will be comfortable. If your approach is "I want it to be original and won't change anything, you need to ride it before you buy. I subscribe to the former with the result that a wide range of frames work for me, from 51 cm to 58 cm seat tubes. But some of them look a little strange. (Ask Robbie about my 93 Bianchi Campione)
If the TT were 54.5, I wouldn't be concerned. But what I'm hearing is that the 21.5" frame (i.e. the 54.5cm frame) has a 56cm TT.
I'm not worried at all about what parts it takes or originality. I've been looking at some built bikes but would change what I need to. I've also been looking at some frame/forks and would build them up with modern parts I have on hand. Either way, that doesn't matter.