Okay, I know its not technically prog but when it comes to 70's technical, worked out music I always go for my Zappa collection. I know he used a few different bassists during the 70's but if you listen to something like "Waka/Jawaka" or "Roxy & Elsewhere" you get the same complexity of prog rock that you get from Yes or King Crimson. But as far as bassists from that era, hands down Squire is the man.