The headers are made the same way, left is left and so forth. If the headers are on backwards there is no way the sidepipess will line up at all, let alone the headers! It is not unusual for the opening to come within a 1/2 inch of the bottom of the front wheel flare. Don't like it but that is where many of them fall. Only use the "scribe lines" for reference-on ALL the cutouts. The only ones that seem to be right-on are the defroster marked cut outs.
Just my 2-cents again.
DV
The white marks you see are just polishing compound, here the header is actually hitting the fender. Cut out by my Ex-partner. I will open this up a little more. Right now there is alomost 5/8's of an inch of the fender not cut out to the actual flare. Ideally the cut out for the side pipes will be just at 1/4 inch at both ends. This was done by cutting on the scribe lines!
DV
PS. Look carefully at the rear, (very dark in the picture), it is cut almost 2"s to much!