Kevin,
The information you’re getting about the shim being on the passenger side (left hand drive) is correct. It looks like the shim you have still has the original tag on it. If this shim was never on your car then I might suggest “loosely” bolting the rack to the car via the brackets on each side.
If you where to tighten the bracket on the driver’s side (LH drive) just to snug, then look to see if a gap existed between the rack bracket and rail on the passenger side. If there was one, measure it to see if your shim is the correct one for your car. If so, install the shim and snug this side.
If the dash is in, slide the steering column and shaft into place to see if all the other point line up along the way (upper bracket, behind dash). If this all looks good and bolts will line up then tighten the rack brackets and turn the steering wheel to see if you feel any binding. If no binding is present then…you’re getting closer to completion.
Dug