If your running the the flex fan and have a new 3 row radiator it should be enough to cool the engine (a fan shroud would be a bid help.

If it's heating just going around the block, and at this point I would replave the thermostat which may be enough to solve the problem.

If the thermostat has been grossly overheated it may be bad and the real cause of you problems. Before you install it, drill a 1/8" hole in the flange where the gasket will not cover it. This will allow any air to bleed out before you fire it up.