The fuel tanks can be an issue, DRMO has them empty and they suck humidity, leading to rusting. Sometimes BAD rusting.
This will lead to frequent filter changing and lots of headache if not cleaned out FULLY.
First, if you can get them hot tanked, DO SO. The solder joints may fail, no biggie since they are riveted and can be resoldered. If the tank ends up with pinholes, these too can be fixed with solder or welding. I prefer welding as it is tougher and is the best course if dealing with extensive corrosion.
All the fittings can be removed by desoldering and removal of the copper pull rivets by drilling. McMaster-Carr has the copper pull rivets. Pulling the cap boss/strainer bracket will enable full inspection and scrubbing to remove all scale. In mine, the corrosion was the pitting form, making 1/4 inch divots on the inside. I drilled these out to full thickness as chasing thin metal is no fun.
Since most of the holes were on the bottom, I taped off the top openings and back-purged the tank with argon before welding. I used thin 0.023" MIG wire as filler with TIG process. You can do the same with MIG, should work fine. It took me several tries to stop all leaks and make it look good inside and out.
Once the welding was done, I used hammer and dolly to make sure all fitting boss areas fit well, then cleaned and riveted the bosses back in place. Flux and solder sealed all fittings and all weld areas were coated with solder for corrosion prevention on the outside.
Now, to stop corrosion inside, I used a fuel tank sealer from POR, similar to the Paint Over Rust product. The entire inside is coated per the instructions, I used plastic plugs on all the pipe thread bosses to keep the threads clean. The excess material was drained by puncturing the bottom plastic pipe plug.
After a year, the tank bottom is sill clean and gray as seen through the fuel. The MEP-002A starts and runs with ease. Aside from the air filter restriction indicator missing, it is fully operational. I don't ever plan to operate it in a dust storm.