What headers will fit???

I mentioned this to him before we finished with headers and he insisting it is not a big deal and will only effect the header install....and he says if anything it should better for handling for moving the center of engine weight towards the rear of engine bay for better overall vehicle balance

though he is right that a better weight distribution makes for a better handling car it sure sounds like an excuse after the fact to me
if it were my car, I would tell him he made a mistake and he needs to own up to up
the only proper way to fix this is pull the mounts, put them on the right spot and reinstall
if that means he has to redo work he did before with the radiator support (which also sounds like a load of nonsense) and pay to have a new driveshaft made, so be it
if he were my son I would call it tuition