Here are some temp readings that I took on my 454, using non-contact temperature gun:
3pm, 26 June (so towards mid winter). Car hot after a 1 hour run, and idling in garage ...
Exhaust headers 510F
Top radiator hose 175F
Bottom hose hose 165F
Radiator top tank 165F
Engine block - various locations 164F
Temp gauge on dash halfway between 100F and 210F and steady, i.e. approx 155F.
Original GM system, except 7 blade fan. All original cowlings in place.
Thermostat has bypass hole through it.