Hmm, I thought Scott wanted to turn the input shaft of the speedo while it was
out on the bench, and figure out what the gauge should read.
I'm pretty certain (the TR is at home, I can't go out and check) that there is
a "ratio" encoded on the face - look under the center portion of the needle and
see if that gives any clue. Oh, no - that's the tach. Look for a number around
1000 (within a few hundred) that will give "turns per mile". That's the missing
piece you're looking for. I have a table somewhere at home that has the values
for various cars and combinations of rear end ratios; I'll find it and send it
along. It should be fairly obvious.