In light of the demise or at least absence of Vintage Centurion site, I'll take the liberty of copying something I wrote in a different thread that I presumed to be true.
Since I (peruano) have an earlier bike (78/79 ecotone) with center pull brakes and braze-on posts, I may have extra clearance as you suggest. Its the Pro-Tour 15 that got the cantilever upgrade.and might suffer the limitation you point out. The vintage Centurion site does a great job of letting you determine what features were offered on what years. There were three basic flavors of Pro-Tours. If I recall correctly, Prior to 79 (double crank and braze-one center pulls); 79-82 (triple crank and braze-on center pulls), and 83 on (with canti brakes and a triple crank). All Tange 2 frames. I can't recall about all of them having vertical dropouts but I'd guess that is the case.