LLY with mind buster fuel leak(s)

Hey guys I’m looking for some help for a friend, he just purchased an 05 LLY previous owner had it as project restoration, any who long story short the guy had swapped engines but while it was out he did head gaskets and had sand blasted powder coated and painted most of the drivetrain. Now when my buddy pick the truck up it seemed to run fine for a couple days when he noticed fuel smell which led to a fuel leak which turned out to be couple hose clamps loose on a line that goes from rail to rail in the valley. That all got fixed alone with a bunch of other random things the previous owner forgot to do. Now after that truck ran good no leaks for bout a day then he noticed more fuel dripping which turned out to be a return line so both got replaced then it was noticed after that the injectors were still wet and appeared to be leaking, fuel was and still is pooling up in the head valley where the injector passes through the head and runs down on To glow plug and over everything else. There was one cylinder that appeared to be leaking more than the rest at the time, the injector was changed and the leak appeared to have stopped. Just this past couple days I’ve been helping him out tryin save some shop time and I pulled the two rear most lines on pass. side and noticed the lines that were powder coated had been completely sand blasted but was still some rust on the threads not much but enough you could notice it and made it tricky to twist off with two fingers. So I cleaned them up with some red scotch bright added a dab of no seize and reinstalled them and brake cleaned all the injector valleys I’ll call em so I could confirm which ones were leaking. after I started truck no visible leaks until you load the truck or rail pressure reaches 8k psi and higher obviously higher psi more fuel leaked. I’m completely at a loss here I think it’s the lines but his dads shop thinks might be the injector body leaking I just find it hard to belive all the injectors have the same leak some a tad worse. Dose any one have any ideas or need more info please let me know soon as you can. TIA all the help and ideas are appreciated I know Im missing some stuff just thought I’d try and get enough info to get some ideas flowing.