I think the motor fitment ring has a taper. This may have made the fit a little tricky.
Always wear a professional grade automotive paint mask when you do any work that creates aluminum dust or filings. Aluminum dust is something that you do not want to inhale.
You should put some 242 on the adapter bolts also. I just did some maintenance on mine and the adapter bolts had loosened on one side despite my lock washers. I’m switching to 242, discarding the lock washers.
I ride (for a year now) 6" pneumatics with 58KV china DD (rear only) and it works fine for me. So my suggestion would be to get a single set and get a feel for it, if it feels underpowered get another set and make it 4wd.
You will need a parallel harness. You connect the main portion (I don’t know the correct term) into the battery and then the other two ends will split to go into both your escs.