What are proper materials to seal furnace

[Fugitive861]

I removed the furnace in our rv to clean and inspect. It looks like it may have leaked water in the past. I’ve reinstalled heater and it is working as designed. Next is to install the exterior sheet metal cover and the two vents (intake and exhaust. What is the proper material to seal the sheet metal cover? There was foam weatherstripping on the inside of the cover. Replace with new weatherstripping or use butyl tape? There was no sealant around edges of sheet metal cover. Leave that way or use Proflex sealant?

After the cover is on what seals between the intake/exhaust ports and the cover? Gasket, butyl tape, Proflex?

Photos are just for reference.

Thanks

[avfordguy]

Reseal with new oem components

[jacwjames]

I used Proflex to seal around the edge of the exterior cover.