I am also sure that the end float is not a problem and have never heard of any form of shimming. The mileage that you have done also suggests all is OK.
If you're concerned, you could put some blue on the cam lobes in turn to make sure that things are running in the right place.
The cams do seem to run against the thrust washer. I don't know though if this is only due to the helical tacho drive. Lots of people remove them, don't they ?
By the way, has anyone ever stripped an original or non-specialist rebuilt motor and found any shims on the mains ? I never have. I seriously wonder if the factory ever did it.