If it was me, and this was my first car interior, I would get ready made carpet and the insulation that comes with it from a place like Auto Custom Carpets. CLICK HERE
There are others on line. I had a customer bring me pre-made carpet and jute padding from them for his '53 Chevy, and it worked out real well. I had to tweak it a little, but it went in just fine. I also bought carpet from them for a 77 Corvette, and that worked out good too. It's also reasonably priced.