This isn't exactly vintage, but close enough.
I bought this Specialized Hardrock Katrina frame (sticker says-Chrome Moly main tubes)(1989-1990 vintage according to you folks-thanks)-with a suntour rear derailleur,a Sugino crankset,cheapo pedals, an unknown BB and a little bit of front cantilever brake.It was a fair price-$20-on both ends-you can buy a complete hardrock in nice shape for $75-$125 in nice shape or so.He threw in a bunch of old Katrina wheels.
I put a Katrina Cane Creek front wheel,an old Shimano stem shifter(works great!!) some other parts on. I then was looking for a front derailleur. I had several mountain FD, but they would require shimming-34.9 and the seat tube is more like 1.13"(28mm I think). I have 2 of these old 10 speed(2 chainrings) SunTour Cyclone 1978 vintage derailleurs. I didn't think it would work because the cage is kinda narrow, and I didn't think it had enough travel to span 3 chainrings. I was wrong-it works fine!! A BIG WEIGHT WEENIE PLUS-it weighs just 97 grams vs 130-160 grams for XTR-or LX front derailleurs.
Sun Tour made nice, inexpensive,reliable, very light" stuff"-.Versatile to it turns out.
As pictures-lights,kickstand-it weighs~26-27 lbs