At first we thought he could remove the tank and bring it to his shop to rebuild it. After examining it via the exploratory holes he decided to disassemble it on site. He removed the outer skin of the tank in two halves. The outer skin of the tank was in excellent shape and we were able to reuse it. This saved a lot of time and material. The fire box was 16 gauge sheet metal (according to the welder) he replaced it with 3/16 thick boiler plate which is the same thickness as all other plate material originally used to build the boiler. He could not find boiler tubes the same thickness as the original but found some with same exterior dimensions and thicker wall. So the heat exchanger walls are thicker than original also.
I had the welder make two modifications.
1. replace the 1” piping connections on the back of the tank with 1 ¼ “ connections now all connections are 1 ¼ “ threaded pipe.
2. weld a deflector on the inside top of the door frame to keep the creosote from accumulating next to the gasket.