ok guys im new to this so bear with me!!! I'm currently working on a 69 mach 1 at the body shop. This car has severe right front damage, I have replaced both floor pans, both lower firewall peices, and Im currently installing both rails/fender apron assembly had it all "squared" by the measurements in the manual. so i decided to hang the fenders and holy **** the fender is overlaping the door by about an inch so i moved the rail/apron assembly out to where the fender lines up to the door and now the motor mount is too far forward and theirs a gap between the firewall and apron that i could throw a chicken thru.The fender bolts right up to the apron. Maybe i got some wrong parts??? I've checked with everyone I know and nobody knows anyone else with this year model car in my area. This thing is eating my lunch the parts I'm installing are new parts, just wondering if anyone else ever had issues like this or am i the luckiest guy in the world. also is their anywhere i can get some upperbody measurements.

 

Also what year models are the same as this one eg. fenders, hood,firewall,rails,apron any help will be greatly appriciated, I'm ready to get this back on the road.

 

69-70 is the same body style minor trim differences

 

Just curious is it a 1inch gap between the curved part of the fender from the door or the straight parts at the top and bottom? Because on mine I noticed the aftermarket fenders are slightly very slightly different from the originals. I fixed it by changing the front a little bit so that it slides back a little bit farther. Idk that was just me though. Was not a professional job but it looks a little better to me lol.
Someone else might be able to comment better on this.

 

First you have to ensure the engine and suspension mounts are in the right location. You cant go turning the engine in the bay, things go bad quick when you do that. The wheels need to be in the right place or you cant get it aligned properly, and it will dog track or eat tires. A car hit hard offset in front is going to be a nightmare to line up, the unibody will be tweaked front to rear like a trapezoid. Check for ripples in the C pillars and quarter panels, if there arent any then its just a stacking of tolerances causing your alignment problems.

You probably already know most of that, its mainly for others reading the thread who might be contemplating a similar repair. When you replace the front end on a Mustang or any unibody car of this era, you tack weld the parts on, then check for panel fitment. That way you can move the stuff around and get it to fit decent. The more you have to remove, the more you will have to bump around to get square.

The fenders cover up the top rail on the engine bay aprons and shock towers, you can drill new holes in them if they are off and it cant be seen later. What I usually do is mock up the front with tack welds, then temporarily bolt the fenders on using the doors as the locator point. You also need to install the hood, front bumper, valence panel, and grille to make sure it all fits. Elongate the holes or drill new ones as needed, you can always weld up the holes that are in the wrong spot. Dont drill anything before it is mocked up, fit whatever bolts you can in to get the fenders and hood to hang, then make adjustments.

Its quite different from the cars built today where you cut out a section and weld in another. These take a bit of finesse and moving parts around, and aftermarket stuff doesnt always fit right. I had a half inch gap on the quarter of the 71 Mustang, the wheel well was in the right place, but the fender was stamped off half an inch. So it was long at the rear, and short up front. Those are the things you deal with when working with these old cars, parts dont always fit right so you make them fit and its more of an art form than a science.

 

Some parts are the same, 69-70, some are not. The fender aprons are the same, but 69 and 70 had different radiator supports.

This is repro fenders AND repro doors:

 

THUMPIN455, I agree in the importance of the engine mounts and wheel placement thats why when i had it well within specs i welded the rail/apron assemblys in before i fit the fenders way more important for it to drive right than for it to have a couple extra holes drilled in it, When i get there this evening I'm gonna put the rail/apron back where the manual says it goes and try and "cheat" the rest of it out. also gonna hang hood and valance before welding. It's possible the top/mid of the firewall may be back some. I'm use to working on todays cars and they dont usually have a half millimeter tolerance if that. The car is currently on a blackhawk frame machine and im also using blackhawk measuring equipment.