Ok, so I did a little thinking outside the box here. I have a set of 130mm spaced wheels sitting in the garage. So what if I bought a 10 speed Shimano cassette, a 10 speed chain, some cable stops and this Microshift Centos mini group:
New Microshift Double 10 Speed Centos Slv Group Set Shimano Compatible | eBay
I assume I should be able to bolt those parts on and use my existing 600 double crankset and have everything working fine?