The FAQ section has a bunch of options. My recommendation is the 73-87 crossmember swap, which will get you to a 5 bolt setup and then you can get replacement 6 bolt discs from places like Summit or LMC.
Here's the FAQ link. It's the best resource on this forum besides the search function.
http://67-72chevytrucks.com/vboard/s...d.php?t=646002