It hasn't been a good couple of months for me and my GS500.  First I decide to replace the base and head gasket to stop the bike's oil leaks.  This resulted in a cracked cam journal when I removed the bolts (p.o. must have overtorqued them).  So I dropped some money on a used head with cams. Today I tried to install the said engine head, and after all of my work, I find that the valves are too tight with even 250s installed.  So what's next for me?  Do I need to remove the head, then the valves from the head, then replace the valve seats? 

They can surface the valves on top as well as cut a 3 angle job and you would be needing thicker shims, however 250 aint no thing, you can get shims all the way to 215, after which you can shave em with a belt sander push comes to shove. Shims are not reason to stop using that head.
Cool.
Buddha.

Good to hear.  I've got extra valves and shims from my old head.  Could I just transplant the valves to the new head?  Also, I have 4 spare, new valve seats.  Could I just replace the valve seats with new ones to regain clearance?

no...he's saying get smaller shims. Try 240's

I should also mention that one of the valve buckets sticks up high enough to where I can't get my Motion Pro shim changing tool to lower the bucket. Not sure what to do about that.

Just tried to put in a 230 shim (the smallest I could find) on my left exhaust valve, and I can't even turn the bucket with it in there.  Does anyone have any advice on what to do next?  I still have my old engine head if parts can be scavenged.