S54/E153 mount compatibility?

The U-shaped bracket that bolts to the front of the transmission is the same part number NA or turbo.

The front and rear chassis side mounts (with the rubber in them) are different part numbers, but I think the only difference is the amount of rubber in the mount - the turbo mounts are more fully filled to provide better torque damping. So try your NA mounts on the front. If they don't line up, then you'll know the difference between the turbo and NA chassis side mounts is more than just the rubber insert.

The drop-in inserts that Kirkosarus used to sell - they just filled the air gaps in the OEM rubber - were different because the NA and turbo had different amounts of rubber.
What kind of inserts are you thinking of? I thought the only ones available now are ones that fully replace the OEM rubber part and the metal bushing.

Those are ones "which fully replace the old rubber." Expect more NVH transmitted into the chassis.