Small update. I scrubbed and cleaned the heater box. There was still a hint of mouse piss, so I painted the areas the nest was in with oil based paint. So far, no more smell. Then I cleaned all the roller lifters so they’re ready to go. Also, my M1 intake showed up this morning. I’m overly happy with the condition of it. I was figuring I’d have to bead blast it and seal or paint it, but it’s so nice, I’ll lightly clean it and run it as is. Just waiting on the machine shop now......