Could my 340 block be filled?

"If my new thermostat and radiator do not get my factory temp gauge to hold steady around 1/2 way or just below what else can I pursue as the cause of running hot?"

To me the factory temp gauge is suspect. My 440 Demon shows 3/4 on factory gauge which has a new sending unit good grounds to the dash etc, the auxiliary VDO gauge and the Sniper EFI handheld will be showing 185 which is the thermostat I'm running. I'd put or at least temp install an aftermarket gauge to verify before hitting the panic button.