I need to buy an engine for my Ford F-150. Low on money so I'm headed to the pick n pull near me

I need to buy an engine for my Ford F-150. Low on money so I'm headed to the pick n pull near me. Truck has almost 300k and blew head gasket I'm mechanical inclined but I need to make a list of things to check for to make sure the motor is in good shape at the wrecking yard. Can someone write things I should look for? If it helps early 2000 5.4 engine.

? Why would you be trying to buy another engine if you only have a blown head gasket?

Replace the gasket.

I want to replace the motor not the head gasket! Don't freaking piss me off!