Hub drilling

Probably shouldn't be changing the subject here but I see disc brake conversion kits all over ebay.... Are the used sets from swap meets just less expensive or have people had issues with the ebay kits. I did a quick search but didn't see any mention.
most of the disc conversion kits are based off of the 73~76 factory set up. almost none of them include the upper control arm, so you're on your own to source those or use your small ball joint early arms with an adapter for the balljoint taper.

almost none of them supply the right lower balljoint bolts, so if you're running a swaybar expect to make adjustments there.

beyond that, it's a drop in swap and all the brake stuff is widely available-- caliper, discs, etx.

the repopped upper control arms come in and out of availability and run about 240+

you can save some dough buying used and then you get to select all the balljoints and bushings you want instead of just whatever comes with the kit. if you're going to buy new, get it from doctor diff. cass is a good dude and sells good parts. 10.95" Front Disc Brake Kit (Stage 1)

now would be the time to thing about whether or not you want to upgrade the entire front to 73~76 if you're going that way. k-member, lower control arms, steering. so that it's all the same system.