I'd start with the outer piece, most everything else can be fabbed as needed when it's opened up, and yes, some paint [and high zinc weld-thru primer] would be very useful inside that area
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics