Been on my back under the Blue Star this morning - freezing it was too! 1. This is as you say crankcase width which is on mine 4 1/8 inch. 2. Difficult to achieve an accurate figure without removing the rear wheel, but you will be very close at 6 1/8 inch. 3. Also governed by the crankcase rear through bolt, but the bosses for the brake rod (a couple of inches to the rear of that bolt), are 4 1/4 inches apart. Personally I would base measurements for 1 and 3, by fitting the bare engine crankcase in place. I have used fractional imperial units as I believe that is what would have been used at the time. Hope this helps. PM me if you need further details. Malcolm.