If you have a good 5-speed SunTour freewheel body, you can probably find larger low gear cogs for it on eBay and perhaps around here. (I might still have some unused 32 or 34T cogs on my pegboard -- I'll check). Then, with a couple of chain whips or a chain whip and a freewheel clamp for your bench vise, you can swap cogs as desired. Pastor Bob may be able to help.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069