[dsraven]

when you get serious about the mustangII front end, check out heidt's "understanding independent front suspension" in their tech section.it outlines what the geometry should look like and why. understand also that the digital level used for installing the cross member should be set on the lower control arm pivot bolt, fore to aft, in order to get that pivot level to the ground. placing the level on the cross member leaves room for error because the top of the cross member may look to be in the same plane as the shaft but could easily be out several degrees. (use a length of rod the same size diameter as the pivot bolt but longer so that it can be left sticking out of the cross member far enough to get the level on it).
so,
check frame for square and straight. corner to corner etc
get the frame at the desired rake angle
level the frame side to side with digital level, placed on top of a long straight bar if you only have a short digital level
block the frame securely in that position
mock up the cross member with axle center line in the correct place for wheel fitment to the fender wheel opening
tack it in place

post lots of pics, we all like to see what you are doing.
mock up the front end and place a wheel on to see if you like it