[greglepore]

First, the spacing of the rear dropouts is likely 126mm-more modern stuff uses 130mm, so you'd have to cram it in-doable, but makes tire changes a pita-or have the frame cold set-so an upgrade to more modern equipment is not a non brainer.
42x24 is a 47 inch gear, I'd aim for 42x27 which is exactly equivalent (41 gear inches) to a modern 39x25, which while not low, is probably low enough. The 52 x14 is a little low on the high end, a 12 would be better, but that's quite a spread on 6 spd. I'd favor the low end