After replacing the thermostat, fan clutch, radiator hose and rodding the radiator I finaly bought an aftermarket temp guage. This helped me discover my factory gauge was reading 20 degrees too hot. So my 454 wasn't running hot, it was still within acceptable range when going uphill.
On another occasion of high temp problem, I discovered the fan clutch I installed a couple months earlier had gone bad. I bought a heavy duty aftermarket model and haven't had a heating problem since.
I also discovered a wonderful product by Royal Purple. It's called Wetter Water. It works as advertised to keep your cooling temps low even in high outside temps and steep grades. My engine runs 20 degrees cooler when climbing a steep grade.