you really dont want to repurpose a gimbal that can support a 1DX and an EOS M
they are two very different gimbal sizes.
For the 1Dx, you need the DJI Ronin or Moza Air
for a smaller gimbal, there are a lot of options. 1Dxii on a gimbal is a disaster in the making IMO. I dont think you know what you're getting into, it's kind of like your camera. You didnt buy the 1Dx first, you probably worked your way on up to it. Gimbal workflow can be slow, or it can be really fast and should be taken into consideration. 1Dxii + gimbal + travel = bad combination. Setup will be very slow, packing very difficult, extremely heavy, external microphone a must.
Those guys on youtube that run 1DXii setups have to be using some sort of roller bag everywhere they go. My A7 gimbal combo weighs in at 5.5 lbs, and I know that the 1dxii combo, decked out to the equivalent, would weigh 10+ lbs. 5 vs 10 lbs means you'll get fatigue much quicker, as the holding position is awkward, which makes it harder to handle than the weight suggests.
Sony A7siii/A7iv/ZV-1 - FE 24/1.4 - SY 24/2.8 - FE 35/2.8 - FE 50/1.8 - FE 85/1.8 - F 600/5.6 - CZ 100-300 - Tamron 17-28/2.8 - 28-75/2.8 - 28-200 RXD
Panasonic GH6 - Laowa 7.5/2 - PL 15/1.7 - P 42.5/1.8 - OM 75/1.8 - PL 10-25/1.7 - P 12-32 - P 14-140