Most panels require several stamping and bending processes to complete a fender. There are also several welded peices attached to the fender. The slightest variation in one or any step of the process can effect the fitment of the part. These new cars have eliminated all of the sub attachments that the cars of the seventies had attached to the fenders. They are no more than skins,held on with plastic hardware,that are simple to produce. Things like light fixtures are now connected to the grille/bumper assemblies not the fender like back in 1970. These parts are complex to reproduce,and most are templated from parts that have been on cars for 40 years. These parts have been stressed to the car they were on,and may have had repairs done to them over the years. I have had original fenders that fit fine on one car,and wouldn't align on a different car without modifying or tweaking them. Trying to make parts that you can take out of the box and bolt on everyones 40 year old cars,that have been bumped around,rotted and improperly repaired.is a daunting task. I'm glad companies like AMD have stepped up to the plate to make quality reproduction sheetmetal parts for our cars. I remember when there were no aftermarket sheetmetal parts available for Mopars.