I'm in the process of tracking down belt material for the main drive belt. I stopped in on our local supplier Empire Rubber where the crew there presented me with a bunch of great info and options. Good guys and a good resource. With their help, I should be able to match the lacing and material.
The belt that I ended up using was:
Empire Rubber's item number: 20045012
Description: 4/140 II Tan FSxFS 1.5" W
Flexco Clipper Lace was used, added to trim length of 78.5"