I would start with a pressure wash, or at the least some Castrol Super Clean, a parts washing brush,and some elbow grease. I just replaced the box on my 86 K30. It was a little bit more than twice as much to replace it than it was to reseal it. Plus it was allot less work. Problem I ran into is I ordered it by application. Got the wrong box. Got it all torn off, had to reorder it, got yet another incorrect box. Gave NAPA the old box to compare. Turns out it matched the box used up until 79! Got the correct one to match, and popped it on in a couple hours.