Don' think you will find carpet or headliner pre-sewn for a hot rod.
I like to use 1/8 PVC sheets for my panels. The last I bought was 22 dollars for a 4 X 8 foot sheet. May have gone up a bit by now.
Search the interior forum. Dan TwoLakes did an excellent thread on this very subject. Go to the Interior Forum, then Tutorials, then Door Panel Tutorial for some good instruction.