New build overheating

[Mayo15]

New to the forum and may be posting this in the wrong section.

I have been going through a nightmare with a rebuild I had a shop build. Long story short I asked the shop to build a stroker motor for me only to find out they didn’t. I was told the machine shop wouldn’t warranty a stroker so they just went .20 with a mild cam, and port matched the intake runner. Then after picking it up it overheats under any type of load. I send it back to the shop who has replaced all cooling system parts and pulled the head gasket and replaced it. Still has the same problem. I was told the head and block were magnafluxed. My question is has anyone experienced anything like this where a new engine overheats under load. What is the mechanic missing?

[Cheromaniac]

What do you define as overheating?

[mpgMike]

If the build included a new water pump, it may be spinning backwards. 1995 and older rotate counter-clockwise; opposite of the crank. 1996 and newer rotate clockwise, same direction as the crank.

[Cheromaniac]

If the build included a new water pump, it may be spinning backwards. 1995 and older rotate counter-clockwise; opposite of the crank. 1996 and newer rotate clockwise, same direction as the crank.

Nope. The water pump on all '87-'06 4.0 engines rotates counterclockwise.
@Mayo15 Which cooling system components did you replace and with what?