Overheating

Did you have the heads milled/shaved?

The heater core won't cause the overheating problem

but I took the center head off and was able to pour water thre the heads which came out the thermostat hole, have I got the head gaskets on wrong.

The center head-you're probably talking about the intake manifold.

It suppose to come out from there to go back to the radiator. Double check all the hoses going to the radiator and resevoir end to end make sure its not plugged-up.

Check the fan clutch by doing this: start the truck up till its warmed-up, then shut it down-turn the fan by hand some drag will be present-if it freewheels easily or locked-up replace the fan clutch.

Remove the thermostat run the engine without it-overheating still present? If so put Stat back and do the above mentioned.

In conclusion if it persist-have it pressure tested to include the Rad cap.

BTW did you find out what caused the overheating to do all these damage.

Check the catalytic converter, if it's plugged up thhat can cause back pressure whhich can blow the head gasket and cause overheating.