I'm going to beging restorating the interior of my '71 Cutlass Supreme and was wondering what would be the recomended grit sand paper to use to sand it down to bare metal?

 

If you are talking about the metal dash, you would want to start with 80grit to remove the paint, then finish in 180grit to give the metal a smaller "profile". Most primer/surfacers can fill a 180 scratch. May want to use an etch primer first, before a filler primer/surfacer. Or use an appropriate DTM(direct to metal) primer or epoxy, though these products can tend to be pricey!