The machines are oldies but more than capable of handling this. The lathe will swing 14" and the DRO on the Cincinnati makes the bolt holes a piece of cake. These will be 2.5" spacers milled from 6061 aluminum bar. As I suspected that hub must be just barely over 8". If I used 8.5" bar I would wind up taking almost a 1/2" off the OD so I think I will use 8". The PCD is 170mm which leaves a .25 shoulder on outside of the bolt holes - the extra 1/32 will never be missed. I can get two 2.5" x 8" slaps of 6061 for $192 delivered by the end of the week. The BORA spacers are double that .Wow, you must have some serious machine tools! That is a big chunk of steel.
I will measure anything you like but to begin:
OD is 205mm. I measured 8.072", I don't have a metric caliper that long.
The 7 on your bolt is not a standard marking. Its a Kubota identifier and best I can determine by looking at the fasteners on my tractor it corresponds to DIN 8,8. DIN 8.8 is 800 MPa (116 KSI). The loader hardware is all marked 8.8. I think I will go with two studs like original made from B7 metric threaded rod (120 KSI) and 4 longer cap screws possibly 10.9 The fasteners are adding another $75.