shimming valves on a new to me "used head"......where to start?

hey guys, how's it going. so bought a lightly used GYTR head for my 2011 yz450f rebuild. low and behold, when it came it was missing the cam circlips and the valve shims from when the POPS employees disassembled for pictures. so now I'm left of trying to guess what size shims go in there. I tried not putting any in so I could check clearence like that for a reference point, but I don't have a shim large enough (and I have more than a few sets), so then I took my old heads shims and put them in hoping I could get a reference point, but the clearances are way to tight even for the smallest of shims. so I was wondering if anyone here has any idea how to make this easier because I have the shim kit coming tommarow, the head was supposedly only used for an hour or so of dyno runs. is my best bet just to guess, check, and reshim as needed?

Install a small reference shim in each position, snug the cams down lightly with no chain and without running them to full torque, and measure.  Correct as needed.

 

In case you're wondering how the factory does this, they have a custom gauge for the job. 

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