The SRF 3 is great, I also retrofitted one to a track frame (see link in my thread about my Mercier). An alternative to a trigger or bar end shifter is to mount a thumbshifter on the stem, like I did.
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1964 JRJ (Bob Jackson), 1973 Wes Mason, 1974 Raleigh Gran Sport, 1986 Schwinn High Sierra, 2000ish Colian (Colin Laing), 2011 Dick Chafe, 2013 Velo Orange Pass Hunter