Regarding the center to center holes......I drew a straight line up from the hole in the front mounting bracket, and then back to the center of the anchor hole at the rear. If you are just measuring the holes center to center, then that explains why your figure is higher than mine. The parts for that Miller dynomag (same as what I have on this Comet) would be difficult to find. I do know of a chap here in Australia who might have some spares. I might try and contact him to see what he has, although parts would be easier to find in the UK.