Does this 31mm valve shim look familiar?
 

http://fototime.com/DF6E591970EFFDA/standard.jpg

It’s the same as an older VW and Volvo but I need it thinner than the 3.00mm minimum thickness that is available under VW and Volvo. Need 2.70 and 2.80mm. What other car uses 31mm shims that are available under 3.00mm thick?

P.S. The car is an ‘89 Chrysler TC Maserati 16V and with only 500 16V’s made these shims are long discontinued from Chrysler.

Know a machinist? Have him mill them down to the thickness needed.

I don't know what diameter they are, but Fiat used shims too. www.vickauto.com has them available individually in .05mm increments from 2.55 to 4.90mm.

I'm pretty sure that some BMW engines use 31mm shims. Plus this place lists shims down to 2.65mm for VWs https://www.techtonicstuning.com/PriceSheet.pdf