My opinion is the Pro Mk IV is a thoroughbred, not a pack horse. Yes, it has head and seat tube angles that would be considered "touring" these days, but I'd be surprised if the original owner could get pannier heel clearance with those short chainstays plus the absence of eyelets on the dropouts meant the rack attachment had to have been somewhat improvised. My Pro was set up as a compact double even before compact doubles were cool, using a period-correct 110 BCD crank. That offers saner gearing but still looks "clean". Best to you in the refurbishment.