Centering front rims on Centers ?

It sounds like you're trying to align the front rims after working on tie rods or something?? I've never had to do that yet on a B, but I would say a rough measurement can be taken from inside-to-inside on the rims, 1st at the forward side, then at the rear side. The measurements should read the same, unless there's supposed to be a little "toe-in". You could also C-clamp a straight-edge (something like a 6-foot long 2x2 angle iron) on both rims on the outside, parallel to the ground and then measure the inside dimension at the front of the rim and then at the forward-most section of the angle irons. Once the rims are both adjusted straight, the angle irons will be parallel and the spacing between them will be constant along their length. I don't have any experience with actual settings for that tractor (although we have several waiting for restoration), I think that will get your rims pretty straight. Once you get the rims where you want 'em, then tighten up the tie-rods. I would still verify that they're not supposed to be toeing in a little. Hope I didn't totally confuse you with all the words.