Both of these guns are K frame guns, and it should pose no problem to shoot +P's in any model number marked (post 1957 or so) all steel K frame (as opposed to the smaller J frame) gun wihout worry. FWIW, the M64 & M67 are the stainless versions of the M10 & M15. Both should be great shooting guns that will last a lifetime of +P shooting.
Bill