I've seen some people either go longer anchors /ready rod then use nuts under the lift. Then structural grout/concrete
In my old house my floor was out of level by about an inch from one post to the other. The installer used U shaped shims and non shrinking grout under the low floor plate. He said this was very common. He had various length wedge anchors on the truck. No nuts under the floor plate. The U shaped shims are available from the lift manufacturers.
I have a Rotary SPOA10-RA that is designed to get under low cars. I could see the pad height difference on my lowest (track) car but it did not interfere with operation. My lift arms were level with each other. Columns were plumb and locks engaged simultaneously.
I lifted many full size pickups (including diesel) with it. It was always rock solid.