327 runs hot

I have a 59 chev belair with a 69 327 in it it has been running fine until this year.
after changing the waterpump it now runs hot(exact same pump as the old one). It increases temp with increased rpm until gauge goes right over to hot. I have changed the rad cap,the thermostat(twice), the heat sending unit, flushed the system ,the rad is only 3 years old. I'm at a loss any ideas

This system is pretty basic, so here's some uh... basic ideas. :)
I would suggest burping the air from the intake manifold. You should have some kind of fitting into the water passages on the intake that you can unscrew, then add coolant until it comes out the hole.
Drilling a 1/8 inch or smaller hole in the thermostat will do the same thing.

If that has no effect, look at the basics. Is the thermostat installed backwards? Is the waterpump correct? I seem to recall some pumps are reverse -direction, used for serpentine -belt systems.

So, this all happened after a water pump change? If so, I would think you should look there. To me it just sounds like you're not getting a good flow out of the replacement pump and maybe look for a better pump.