My Paramount P10-9 has a 14-24 cog set and 52-42 rings. This gives a gear range of about 48 to 101 inches. A modern touring triple or mountain bike has a low gear in the teens. I've got a heart problem and I'm worried I'm not going to make it up the steepest section of my commute, where on my MTB commuter I'm at about 30" gearing. But I'm not sure I want to change it either - it wouldn't be authentic, would it? I do see 14-28 5-speed cogs are available and might change for one of those, but it still only gets me down to 41", and I don't know if my derailleur can hack it. I can't find any lower chainrings for this crankset either. I guess I'm just worried that the bike will be overgeared for me and I won't be able to change it without major surgery.

The P15 had a triple and a lower cog, and looks like different derailleurs too?