there has to be a reason the auto manufactures went to the tapered roller design.
This is one of the reasons. Pairs of angle contact ball thrust style races (like the Stovebolt trucks use) and taper roller bearings have a set of load lines running through each race which make a virtual diamond shape looking from the front or back of the axle. Taper roller bearings make a narrower diamond load line pattern than ball thrusts, but as the load is taken across the whole of the taper roller the setup is far more rigid than with ball thrust bearings.
What this means in (hopefully) plain English is that you will get less "rock" on the hub and disc with taper roller bearings of the same size than with ball thrusts. So the potential for disc brake pad "knock back" is reduced with taper rollers. Any brake pad knock back means that you will have more brake pedal movement to bring the pads onto the disc faces when you brake.
Having said all that, well adjusted ball thrust bearings should work perfectly well with discs if the brake system is properly set up too.
BTW, Whitedog, I looked at your photos of your 3/4 ton disc conversion work-in-progress. Those huge calipers should give really impressive stopping power once you've finished the fit up.
