Are you using a disc brake conversion kit?

I'm sure that someone that has done this conversion can clarify this, but doesn't the conversion kit include all the hardware you'll need? The only thing you have to re-use are your old steering arms....which you have on order.

If the conversion kit doesn't include all the hardware, I think that 2 1/2 inch long automotive grade 8 "shoulder" bolts and nuts, with "fine" (20 pitch) threads, would work to secure the steering arms.