The decklid has for & aft. adjustment along with height adjustment. Assuming there is no accident damage the decklids can be made to fit pretty good. I would need to know a little more details to help you, Is the decklid a original FORD part or aftermarket? Is the decklid on the car now?, is the decklid off but the hinges still on the body? or is the decklid and hinges removed?. You mentioned side to side adjustment and there is no side to side adjustment, however if your decklid margins or wide but even on one side and tight on the other side the hinges can be shifted over. With the lid open have a helper (as this makes it easier) and both of you shift the decklid over to the side that is widest. This would be AFTER all your other gaps are good (height and for/aft). If the gaps taper, look at the gap between the upper rear panel and if that is not even, adjust the hinge bolts at the decklid to get that fitting first as that is kind of your base line. Some 69 & 70 model fastback decklids tend to be sticking out past the qtr. extension on one side ( I have seen this on several original cars). You also must consider the corner extensions as they play a roll on the fit as well. I could go on all day with different scenarios, but with a little more info. I should be able to help you out.