Either find a new front end with the right gears, or swap the disk brake parts onto your axle. We did option B on my brother's '70, it helped a lot. You will need: hubs, disks, calipers, caliper brakets, spindles, knuckles, axleshafts, and assorted seals. I don't remember if the bearings are different or not. The knuckles have the same 6-bolt spindle pattern, but it is clocked differently and it won't bolt together. The later front ends (disk) have bigger steering (u) joints between the inner and outer shafts, which is another plus to this swap.
Additionally, you need a disk brake master cylinder and a new proportioning valve. I would use a Wilwood adjustable valve, around $40 from Summit, instead of the factory ones. Plumb your front brakes straight off the master, and put the adjustable valve in the rear line. This will also accomodate a future rear disk swap if you want (thats why my '83 has one).
You should be able to pick up a 1/2 ton front end for $150-$200 at the most. I've got a disk brake 10 bolt for sale w/3.73s if you're interested. I think my brother has a 44 w/ 3.08s. (Colorado)
'83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
'97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd