This has NOTHING to do with your fuel pump replacement , the fuel pump is on the opposite end of the engine.

The shop that pulled the heads is responsible for this leak , you paid them good money take it back and find out what they did.

1 of 2 things happened , either the stud came out of the head when they pulled the tube nut out , or the stud broke off and whomever repaired it did something wrong.

thread sealer needs to be used , assuming the threads in the head aren't all boogered up , but to do this properly the cooling system needs to be drained , the stud pulled and the coolant cleaned from the hole in the head and the stud.

Or use a bottle of Moroso ceramic seal. any of the head gasket/cooling system stop leak stuff has the potential to clog the radiator and/or heater core...