I already feel like I cheated by buying your hubs. I could just about quote you your product lineup I've spent so much time on your site. My only motivation for going away from 5/8 axle is to do something different.
Trying not to buy prefabbed items.
But, this close to the holidays I'm likely to just order grade 8 bolts like you mentioned. I'm definitely going to re-use the spindle I have. Picked up some metal flat stock and cutoff discs over the weekend.
[Edit] Anyone know the width of the BD hubs?
[Edit2] Nevermind. I got the measurements -
Stock bolt 5/8-18, 4.5" long. ~1.75" Threaded.
Thickness of spindle: 1"
Thickness of BD hub (bearing surface to bearing surface): 1.9"