Welp, I finally found the answer. I called Shimano for a third time, and they figured it out. They were giving me hub specs for the newer M760 hubs, even though I specified "Yeah, I need the older M756 6 bolt hubs.". Dumbasses. They were pretty rude, too. So if you need hub specs, my advice is to double and triple check with as many sources as possible (unless you already have the hubs and can manually measure them... even then you should check with a reference).
On the bright side, I get to use the same length spokes for all 4 sides (front and rear, left and right). That's just how it worked out with using disc hubs and offset rims. The spoke lengths all were within .5mm of 291, so I was able to round them off. I get to only buy one box of spokes and actually use most of them! They'll be DT Competition 2.0/1.8/2.0 in BLACK. They come in a box of 72 with alloy nips, but I bought a box of brass ones to use.
On the bright side, I get to use the same length spokes for all 4 sides (front and rear, left and right). That's just how it worked out with using disc hubs and offset rims. The spoke lengths all were within .5mm of 291, so I was able to round them off. I get to only buy one box of spokes and actually use most of them! They'll be DT Competition 2.0/1.8/2.0 in BLACK. They come in a box of 72 with alloy nips, but I bought a box of brass ones to use.