How to replace headlamp housing

I have a 1989 Ford Mustang LX & i cant figure out for the life of me how to get my headllight housing out, i brought a replacement 6 piece set to go in place of the stock light housings but i cant get them out. I see all the screws that hold the light in & like 5 or 6 stick out behind the engine but I dont see a bolt head to unscrew, i jus see a 6 threaded screws sticking out with no head. please help, i want to take the entire headlight assembly out & put new headlight & housing back in.
Fox Mustang Restoration :: Products these are the replacement lights