check with this outfit for material http://www.originalauto.com/ if your going to do it yourself or best way get a quote from a shop that does interiors if your going with a custom interior it could be cheaper it depends on the material used
You can look at the trim number on the cowl. You can then send that to http://www.smsautofabrics.com/. They are located in Oregon. They will have the exact materials. http://www.originalauto.com/ may have some of the same materials but not always. Not like SMS who reproduces the old stuff. SMS if you send your old panels will redo them and you may wait for 6 months. They are around $800 and I think that includes the material but that quote was 3 years ago. I have a 1956 98 and I had a local guy do it for sligtly cheaper but I wish I sent them out. He did not do a 100% job so I will someday have them redone. I am now doing a Super 88 like you and I found a new local shop and they quoted me around $700. Hope that helps