if you have 531 you have one of the best metals ever used for traditional lugged construction of classic bikes. THe only way you will improve your ride is by improving your fit. Look at the geometry and not the tubing, consider custom steel.
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1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear