Overheating issues on a rebuilt 360

You mean the thermostat? Cause if that’s the case I removed it and still gets over 180

No, I mean the bypass. 90° hose between the pump and manifold. Put a 1" NP plug in the manifold, and tape the pump for 1/2 NP and plug it. See pic.20180312_133511.jpg
Also, that 180° stat is where it begins to open. Get a 160° so that it is fully open by 170°