Front end squaring

Hello I'm hoping someone can provide me with some information regarding measuring the front of my 2003 expedition, Let me start by saying the vehicle was in a front end collision and I have been trying to repair it. The old rad support has been completely removed along with the rad A/C condenser, hood and both left and right quarter panels, the entire front end is completely open. Here's my dilemma I am trying to square the front but am not sure from what point I am supposed to using as a reference, when I try to roughly put the pieces together I can see the I have a gap on the drivers side between the new hood and the quarter panel and the on the passenger side the gap between the new quarter panel and the passenger door is to tight. So I need to determine which way to push or pull and to know which side is off, hopefully this makes sense. It's my understanding that there are specific measuring points that are supposed to be used to square the front end I'm just not sure where . Any help or advise would be greatly appreciated.

most body shops have the specs for the frame. you might need a frame pull.

Try a car lot with a 2003 on it. bring a tape measure and some pictures of your front end to write measurements on. Use holes or bolt heads, but be careful of bolts that use a speed nut ( as on fender ) as there is "wiggle room" to adjust the fit of the fender.
Try to use triangulation: Left front inner fender hole to right rear inner fender hole length compared to the left rear to right front length. Be careful of any play in the "hook" at the end of the tape measure too.