Non-indexed thumbies all the way! (I run my 7-speed SunTour in friction mode, which let me convert painlessly to 8 speeds last year.) I am part of a team which repairs donated bicycles every year to donate to needy families, and replacing malfunctioning triggers with thumbies is my standard quick-and-clean/reliable repair. I stocked up on a bunch of thumbies at about $10/pair on eBay.
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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