Mr. Chimpmunk,
You are going to go from ball to tapered roller on the front OUTSIDE only..not on the inside? As Bill indicated above, all it requires is a spindle OD measurement and a hub ID measurement. I am afraid that you might have few, if any, choices on how thick (wide) the combination is.
If you have a Applied Industrial or Motion Industries store near you, you can ask them for a Timken catalog. Its dry reading, but you will be surprised how easy it is to spec your own cup and cone.
The usual question that is asked is why switch when the stock setup has performed well for so long..and your only doing the outer bearing!
Well Mr. Chipmunk, good luck at NAPA and keep everyone posted on this, bearings are a hot topic for old iron.
Stuart