Jeep Strokers

I recently purchased a rebuilt head casting 7120 to replace my damaged 0630 head. When I took it apart for cleaning/polishing I found these spacers /shims under all the valve springs. They read 100 and this side up. I'm assuming the 100 means .100 thousandsth of an inch. The seats appear to not have been cut or damaged so i would guess this is to bring weak springs back to the proper load level. I will be using almost new mopar performance springs from my exixting head..they have about 3 or 4 thousand miles on them so I would NOT reuse the spacers?. If this is not correct what is the purpose of these spacers..thanks

Shims are common. When a valve job is done, the valve sinks into the head a little and the valve tip gets a little higher, increasing the valve spring height and decreasing spring pressure. Shims are used to put the 'valve spring installed height' back to factory spec.
Sometimes shims are used to raise the spring pressure, but you have to watch the 'valve open' spring height so the spring doesn't coil bind.

I don't know what the Mopar spring specs are, but you should measure the spring installed height and shim them to spec.