The pick guards will fit fine, but as mentioned, the 5-way slot is the wild card. A 550 guard will have the narrow slot and might interfere with the #1 and #5 position because of the thickness added by the guard. I use a router table with a 1/4" bit and made a sled that the pick guard screws onto to open the slot(go from 1 screw hole to the other and its perfect). If you're okay with a clear guard, then a Jem FP would already have the slot cut. I've done this mode to several RG and Prestige guitars over the years.