Understand, on the F & F gig.... Don't blame you. Are you sure, that gauge is accurate?... Heater wouldn't exist, in my world, something isn't transferring heat, somewhere.
I had suspected the gauge but I'm also running one of those Mr. Gasket thermometer radiator caps and it agrees with the gauge in the dash. Because the radiator temp is high I must be getting coolant flow through it. I need to figure out why it's not making it through to the heater core. The core was new and the whole system was flushed when I installed the 408. I didn't spend any time on it today.