I run stock thermostat and stock everything else. No problem with heating up. We have a big cruise once a year and you are stop and go for hours in 80-90 degree heat. I have seat in traffic for three hours moving inch by inch. No heat issues.

Get you a thermal heat gun and check temperatures. A lot of time gauges are wrong. Hitting 220 at times should not be an issue on the cast heads and engines. The hot warning light does not turn on till 245.

Timing has a lot to do heat. I run stock timing on ported vacuum.

You lower and upper radiator hose should be different in temps. Lower should be about 165-170 and the upper will be your running temps as it comes out of the engine.

Your oil light coming on could be oil pump related, pre assure dropped and knocking started. Might want to really check it or keep an eye on it.