I have my tank out of my '68 right now. I wanted to sandblast and paint it before reinstalling. The tank is empty. Is this safe to do? Do I need to let the fumes escape for a few days??

If you are concerned about fumes, then fill the tank completely with water before blasting. I would take measures to make sure no sand gets inside also (remove sender, plug hole..gas cap on tight, and then the area taped...etc..)When finished, empty the water out, and let it dry up for a day or two before reinstalling the tank.

I would be concerned about sand getting in and also about getting a bunch of pinholes through the tank. Why not get a new tank? At about $100 a pop for a new one, it wouldn't cost much more than sandblasting your old one.

I dropped mine, washed it out with Dawn detergent and water, dried it, media blasted it, then painted it. There was no gas in it at the time of the washing but it smelled of gas. When I worked at a dealership (ions ago), we would routinly drain them, wash them out, stick an air sucking hose (exhaust vent or dry vac) over the filler neck, and let the air enter at the pickup hole and dry the tank. No fuss, no muss. If it has pin holes, I would rather find them now than after the work is done and 18 gallons of good stuff is in it.

mine had no holes before... was out again in 2 days for a replacement, glad i only put a gallon of gas in it, that'ss all i had to clean up