The shim you found is a danger: eventually it will break up, and you don't want the bits getting into your nicely meshed timing gears. Shims should only be used between components which do not move in relationship to each other. If you want to reduce end float you can lap the timing gear onto the shaft with fine grinding paste, but I would accept your 3 thou without any worry.

Robert Leigh

Location: Cottenham, north of Cambridge

The 'shim' in the picture looks like rubber rather than metal. Perhaps it was an attempt to reduce the oil flow from the cam bearing.
The front bush is very liberally lubricated and overflow from it lubricates the gears.
Often the feed hole is reduced in diameter to stem the flow a bit and increase pressure at the big end jets. However they don't need much and there's so much oil flying around inside an A7 engine I don't believe lubrication is a problem.