340 Overheating Help

I have a 340 that i just had rebuilt. It was bored 30 over, 9.75 to 1 compression, and I am using an edelbrock rpm airgap manifold. I have it in a 72 dart, when the motor heats up the stock dash temp gauge is at the bar before 250, it stays there and does not go past the bar. I put the end of a mechanical temp gauge in the top tank of the radiator and it stays at 200.

I have replaced the radiator with a US radiator 22 inch 3 row unit, i put a new fan clutch (hayden Jag unit), I am using the stock shroud, I tested the thermostat and it opens. I also ran the motor with a different thermostat and no thermostat and the same thing happens.

The motor does not crank when it is hot, i have a mopar mini starter on it.

I took it for a drive tonight about 3 miles an the gauge stayed at the bar before 250 on the stock gauge. When I got home the gauge was on 250.

Any thoughts on this, tomorrow i am attaching a mechanical gauge to the motor to see whats up.

Thanks Mike