Frame mount for a 8A and 8B are the same. Difference between the A&B is the left and right swing set up. Frame mount bolts to the tractor and takes some of stress off some parts of the tractor adds to the strength of the rig . You are close enough to drive over and look at it on a day trip. One note here, it's not for sale. Measure all you want. Sometimes you find them for sale separately, or at auction, and the most I've seen them sell for is in the $4000 range for one in almost new condition without the factory frame mount.
Chris