I removed the dash as I also needed to replace the recirculating flap servo. When I had the box out, I was able to spot and repair some rust forming on the bulkhead panel the fresh air enters through.
I feel taking the HVAC suitcase apart to patch the doors the more thorough option. I covered both sides of the doors in aluminum tape, then adhered thin neoprene sheet to that with contact cement. Trim to fit, presto.
