I redid the interior in my 71 for about under $50. My interior was completely shot. The original red leather would crumble in your hands. I needed to replace the entire interior.
I bought a 4x8 sheet of 1/4" fiberboard
($4.50, home Depot) and cut new panels using the old ones as templates. I got rid of the map pockets. I was missing the rear ones and the front ones were not repairable. The rear panel under the window was the hardest to fabricate. I cut two peices of board and made a canvas hinge to complete the bend.
The new panels were then covered in 1/4" headliner foam(3 yds @ $5/yd) using 3M spray adhesive($8/can). I sewed the pleated covers in vinyl(3 yds @ $7/yd). YOu can check out the new interior at my website:
http://www4.ncsu.edu/~jpnovak
I followed the vertical pleats for my 71. I chose the vinyl for cost. I did not care if the car was completely original. I just wanted to stop the flapping panels. the rear made a lot of noise with the top out and I was tired of getting hit in the head with bits of leather. hope this helps some.
Jamie 71 911T targa