Literally anything would be an improvement. This tank has always been a liability - apparently up in North Sac they use funnels instead of stack flappers to maximize tank crust. I'd totally be willing to coat the inside of an old tank with the red stuff if i can get down to bare metal - I've heard it doesn't stick that well if you still have a coating of rust, though.

the best is a new tank and red coat that so its protected from the word go. or make it out of 308 or 316 stainless.

welding thin section with mig is fairly easy its just less heat i have welded 0.6mm sheet with 0.9 wire you do spot welds not stitches and control the heat by alternating seams so it doesnt get too hot. its easier with .6 or .8 wire. and 1.6 mm and 2 mm welding rods do exist.

it might be worth asking a sheet metal shop to make one for you if you make a template out of stiff card they can use that to make a copy thats the costly bit is making the pattern.

Had to change one settings on my camera to be able to load pictures
Here's a couple of the tank

D2Gary, how rusty is the inside? In your opinion, could it be cleaned and re-lined? Also, where are you located?

Muriatic Acid works well to clean all the rust from the inside of the tank. Gets the entire inside of the tank clean down to bare metal. I diluted 50% with water but others have indicated they use it full strength. It is an acid, and I did mine outside and had some baking soda and water available to neutralize and rinse the tank. I then coated the inside with a sealer. Trick with the sealer is to make sure you let it cure completely, do not rush the process. Got the acid at my local farm and garden store.

Bruce

I'm in north Idaho. I wouldn't have a problem using this tank. Good cleaning and it should be ready to go

You can put a handful of nuts and washers inside shake around for a bit. This will loosen any rust, empty out, then treat. I have done many tanks this way with excellent results.

instead of nuts or bolts use a bit of light chain or dog chain add a cleaner of choice put the cap on and shake vigorously the chain is easier to fish out

Partial filled 1/4" short drive screws. Cleaned every nook and cranny

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D2Gary  pm-ed you on this (I'm new here, so pardon the formality).