Machine Shop Did not Shim Valve Springs

I'm in Mexico, so perhaps "blueprinting" a Mopar is too much to ask. I asked the machine shop to install the new 340 factory style springs with dampers at installed height of 1.650". However, when I picked up the cylinder heads with valves/springs already installed they just told me all the final installed height measurements are not the same. No effort made to use shims to even things out for me.

I built my first small block 50 years ago, but an not familiar with shimming the valve springs. I notice some shims for sale on this forum called '31 VS! 303 which I assume fit a factory unmodified spring seat. Don't know how thick the shims are or if they come in various thicknesses.

Can anyone suggest a thread here that explains what one needs to know in a situation like mine? Or perhaps a video? Thank you. (Cylinder heads are 915 with 1.88 intake valves). Valves, retainers, springs, locks are all new stuff.