Since you're in Vancouver, you might check in with [MENTION=255930]mikemowbz[/MENTION], he works at a bike shop there, has a lot of old parts and may be able to fix you with something both vintage and appropriate.
If not, I've got at least one each AR, Mountech and VGT long cage derailleurs I could send one home with him when he comes to see me in a couple weeks, if you haven't found anything by then.
Don't put anything modern on that bike, your helpful bike shop is just offering you that because that's what they have on hand. You can do better. You have a kind of special bike; it deserves old SunTour stuff.
__________________
● 1971 Grandis SL ● 1972 Lambert Grand Prix frankenbike ● 1972 Raleigh Super Course fixie ● 1973 Nishiki Semi-Pro ● 1979 Motobecane Grand Jubile ●1980 Apollo "Legnano" ● 1984 Peugeot Vagabond ● 1985 Shogun Prairie Breaker ● 1986 Merckx Super Corsa ● 1987 Schwinn Tempo ● 1988 Schwinn Voyageur ● 1989 Bottechia Team ADR replica ● 1990 Cannondale ST600 ● 1993 Technium RT600 ● 1996 Kona Lava Dome ●
Last edited by Lascauxcaveman; 08-31-16 at 10:23 PM.