I think that you have chosen the best option. My thinking though is why did the casting crack in the first place? Check how the mating surfaces of the tank mounting align before you tighten everything up. If they do not sit evenly, face to face, then when you tighten the fastenings damaging torque will be applied to the repaired joint.
I suspect it cracked though someone applying too much weight on the stove or it striking a heavy object like the floor....who knows? its one for the history books....
It’s about 100 years old so I can only surmise what cause it. Regardless, the tank fit check is about as good as can be expected. There will be no extreme tightening of bolts on this stove. I expect the jb weld is stronger than the cast iron and I think the first failure mode from a misaligned tank mount would result in a new crack above the jb weld area. it’s going to take some real artistry to get this to look decent. I plan to spend a lot of time removing the roughness of the jb weld and I may go over it with a body filler type topping to get a super smooth surface, then paint with ceramic glazes. I have about 10 shades of green/brown/black that I plan to test on samples of jb weld to see what comes closest. I’m taking this slow.
best way to practice is do the same on a piece of wood with the jb weld and filler so you get the right base for the paint, that way it will be a lot easier to grade the colour correctly. Create some small swatches on the wood to practice on. its what you see done on walls when you go to paint a house over here, they paint several squares with different colours but all on the same base coat to match in correctly. always interested to see the result please.
That is my exact plan. It’s going to take me some time being that my intrinsic sense of color is far from an artist’s. I’m hoping digital pictures and comparative software to help. As of today, all went well with the bond (typical jb weld). Burner and tank fit dead nuts. This is a first for me using this stuff on cast iron.
@Jesse There is a school of thought in restoration that the new work (or the damage) should be muted but not invisible. And also the school of thought that any fault should be invisible. For myself, I would tend to the first approach here. You don't need perfection, and indeed if this were a museum piece you would be aiming for a washed-out look in the fill: a half-strength, lighter tint. But you aren't a museum, and a close match is reasonable too.
Here’s my repair. Not the best nor the worst I’ve done. My first attempt at airbrushing ceramic glaze paint. Cured with a heat gun and a thermocouple.
Dang! That really came out nice. I doubt anyone will ever know it's been repaired unless you point it out. Excellent work my friend. Ben