Thanks again guys, I figured it was something fairly simple.

The rear that came in the frame I got with the 41 pick up is actually an 8 3/4. It has the casting number 1820657, which from the tech section here tells me it was made between '57 and '64. So that's a plus. It's a little wider than the stock front track width, but maybe it will wind up being close to the same as a Dakota width.
Matt