What do shims do?

If the worst comes to the worst and tipping the stems, fitting new STD valves or any other method won't bring back enough clearance then have larger valves fitted before resorting to new seats or sourcing another head if that seemed the only other option.
The seating area for the larger valve head uses the previously uncut outer area of the seat and will bring the valve head back towards the combustion chamber .
It will restore the stem height to within spec and you will be able to use shims towards thickest range again .
Fitting larger valves is an old solution used for rescuing badly worn seats and is actually the primary reason why many a head has had bigger aftermarket stainless valves fitted rather than for any performance advantage.