When it comes to high-performance road racing or wide-ratio gearing, in the vintage era, nothing kicked ass like a Suntour VGT. As evidenced by this pre-1976 Schwinn Paramount on ebay, selling right now, sporting a super-record/VGT drivetrain :
If you can't find a Suntour VGT, you can always settle for a lesser derailleur, like a Campagnolo Super Record, Rally or Shimano Crane GT... :-) :-)
The Suntour VGT was the true anachronism of the 1970's era - the best-shifting wide-ratio derailleur on earth retailed for $12.95, and it often replaced the worst-shifting french derailleur on earth (Simplex Prestige), which retailed for $4.95. And it outperformed the $35 Campagnolo record piece of eye candy with pure, smooth, shifting muscle.
I remember on our club rides, one of the most "in-the-know" guys showed up on a high-end 531-throughout bicycle with a Suntour VGT, and we all questioned him about it. He was ecstatically happy. The next year, I put one onto my Raleigh Gran Prix, and I shared in his bliss...
That market distortion (price doesn't always equal value) probably is what got me hooked on bicycle componentry ...
- Don Gillies
San Diego, CA, USA