will this one replace the amana oem furnace replacement limit switch 10123519?

Quite honestly it may but I actually ordered it for a Rheem 90 classic furnace. i know from searching that it covers a few furnaces but i cant recall if it was for the one you are looking for. this should be the one for you . 20162904 - Amana OEM Furnace Replacement Limit Switch just make sure to check it with yours.

will this fit rheem 266A?

In order to verify this is the correct part you will need for your replacement, we will need the brand name of your equipment along with the complete model and serial numbers of the unit this part is going into such as a furnace or A/C.

Will this fit a rheem gas model rgps-07eamer ?

This will not work for you, but I have found the part that does. There are actually 2 limit switches for your unit, one is near the burner compartment and the other is in the blower housing, here are links for both. Burner compartment: http://www.amazon.com/gp/offer-listing/B00FFH2MTU/?seller=A3ENSQM9L05QCM&ref=myi_listid_offer ; Blower housing: http://www.amazon.com/gp/offer-listing/B077NQ29JL/?seller=A3ENSQM9L05QCM&ref=myi_listid_offer