Any input on these heaters cores? Now that I have dug into ours, I need the heater core rebuilt/replaced, the bypass valve shown rebuilt/replaced, and the heater control valve at the firewall rebuilt/replaced. For Gary to rebuild my core is $300. I can’t find rebuild kits for the bypass valve so $75 if you go new. I have not found a rebuild kit for the control valve either and haven’t priced new/rebuild kit. I would rather rebuild myself but if these are good quality it kills 2/3’s of my problems.