I need a replacement pump head for a Grundfos 15/60-130 3 speed central heating system. Can I assume that the various manufacturers replacements all conform to the same 4 Allen screw fixing dimensions of about 80mm spacing? I am confused by the various letters applied to the part names that have started to appear like CESA 03, CESA 02, AOKR. Are these some form of energy indication or maybe the connection details. I just want 3 terminals to wire to.