I have recently discovered that I may have rust and other debris in my gas tank.
What's the best way to get it out?

I'd get a new tank and sender. It's a simple low cost job. Why use a 35 year old rusty tank???

I will eventually but I don't have the $$$ to spare! Plus it's been really great weather and I'd like to take for a road trip this weekend.
So I'm looking at doing it either tonight or tomorrow morning.

I just found out the same thing. I wouldn't recommend any road trips with a rusty tank. I've had my carb clog up twice in the past month due to crud in the tank. I have to replace my tank as well. While we're on the topic...which tank and sender do I need? I have a 65 SS do I need a vented/unvented tank?

Last summer I had to have the carb on my '66 rebuilt due to rust in the gas. Thought that I would have to replace the tank. Pumped out the gas, disconnected the sending unit and the gas/vent lines, unbolted the straps and dropped the tank. (No problems.) Turned out that the tank was clean. The sending unit was the culprit. Easy replacement.

Good luck!

Greg

If your pickup tube still has the mesh "sock" on it, a small amount of rust will clog it to the point of killing the engine when under a slight load (BTDT). A quick fix is to drop the tank, remove the sock, and install a good in-line fuel filter before the pump. Cheapest permanent fix is to coat the inside of the tank with a rust sealer made for that. POR has a kit that contains a rust treatment and sealer that works well. I used it and have had no problems in 6 years. It costs about $50-$60 if I remember right.

I bought the POR kit, but I have seen others as well.

Believe it or not, most radiator shops will work on old gas tanks to clean them out and seal them.

You can get new repro gas tanks from many places.

Steve

The gunk that the radiator shop uses to boil out and pressure check the tank needs to be cleaned out of the tank FIRST,,, use a 50x50 Simple green or get a can of por marine clean first
then I used a qt of metal ready to etch then I used por tank sealer. bueno!!
Ps 72 tank I closed up all three vent holes (eec?)
drilled hole next to filler pipe (72 E/C)ran 3/8 tube up neck tapped into neck before cap and run a vented cap, no problems