Two revs of the VME spec are on bitsavers under motorola/VME
I should dig around and try to find the extended version of the spec that added 32 bit bus support.
In the very early days, there was a separate bus controller board that handled the arbitration, that was integrated onto the CPU board around the 68020 timeframe.
I know I had the manual for the moto 131, but I haven't seen it in 20+ years. I'm going through storage right now, maybe it will turn up.