...If you buy a 14 bolt for 150$ then spend another 300-350$ for a disk brake kit...QUOTE]
Or just buy late model 14 bolt that already has Disc Brakes on it.
Not sure about the math, but the 35 spline axles for the D60 will run near 400 for the set. (Unless you luck out and find a rare 35 spline D60 under a van.) But remember, Your spindles better accept the 35 spline axles or you will be paying 250 or so to have them turned out. Some are even too thin for this!
Add an extra 130.00 for the D60 locker. (Approx 490.00 vs 625.00) Still gotta add 100.00 or so for a good diff cover.
Not sure how common discs are on D60s. So odds are you will add disc brake kit. You will want to truss both axles.
Most common rear Dana 60s are simply a Dana 44 with a bigger ring and pinion and bigger tubes. Will work fine for a moderate wheeling rig, maybe up to 38-39" tires. You'll still be pushing the 30 spline axle limits.
If you need strong stuff for serious abuse with 40+ tires. You cant beat the economics of a 14 bolt. The 14 bolts are very common. Quite cheap, still. They have quite larger rings and pinions, combined with the most important feature of the R&P...the front pinion support bearing. The axle tubes are larger. The axle shafts are so strong, you seldom see people upgrading to alloys. The disc brake conversions are under 300 now days for either axle. And once they are "13 bolt shaved" they have about the same or better ground clearance than the D60
There may be 100.00 or so difference at the end of the day. I'd say, if you need the beef, get the beef!
If the 14 bolt wont do it...now yer talkin' D80 or AAM 11.5