i built my own, (im not a rich guy like bagger
) the spacing from the center of each punch is ~39mm / ~1.56in... mine was reverse threaded....
dont mind my crap welding though, the weld held.
The only mistake i made was not to remove the punch marks out with a drill, so i ended up ruining some of the smaller threads, this was resolved by using a matching pitch tap, and rolling it on the bearing till it took out the messed up sections.....