Be careful using plastic it's brittle.I think most door panels are made of a hard board like Masonite. $1000 per door what would he use? Gold.
I tried making seat covers years ago on a 67 Camero they came out OK but I wasn't proud of them. Sewing is hard,a lot to know.You will need a heavy duty machine. Not your wife's Singer.



These old bolts are in my blood. Hard thing is focusing on just one.

1937 Chevy 1/2 ton panel
1953 GMC 2 ton. future car hauler