When I put discs on my HO72, I converted it to the 9/16 studs. I believe for the proper press fit, I used a 19/32 drill bit which is .59375'', within spec for the interference/press fit for the studs that I used.
The studs are a Dorman part, part number is DOR-610-228, and they are good if you are using steel wheels, I found this number from a tech write up on Pirate and they were perfect -
http://www.pirate4x4.com/tech/billav...b_disc_brakes/ . And if you are using aluminum wheels, use Dorman part DOR-610-301. The 610-228's are $1.84 each in packs of 10 from RockAuto.
I personally wanted the larger 9/16 studs, its what the 14b's use, and bigger is better right? It's basically just like doing the same setup on a 14BFF, you need to use the same parts, and after I found those part numbers, I figured the extra time it took to drill out the hubs was more worth it than browsing the Dorman catalog for hours trying to find 1/2'' studs with the correct size shoulder.