Timing problem

I took apart the carb and cleaned it. The new double filters before and after the fuel pump. The one before will be removed but it kept the contaminants out of the pump as the sock was disintegrated. They also kept the carb good and the carb saw bad gas only for a short time as I had just installed it. It was more like contaminated new gas.

The old tank was new 7 years ago so there was no rust in there and on the inside it still is good and galvanize coated. I think. When I say I think. I mean..............the sending unit that is sold is advertised as stainless steel. It is not completely stainless. The electrical housing is plated. The old gas that ate the float and the sock. Also dried up on the housing and ate that coating. When washed the old gas off that sending unit. That part rusted.

I tried acetone to clean the old tank and it didn't touch the dried up gasoline. I did put new gas in the tank. 10 gallons of it. It didn't break up the sediment of dried out 7 year old gas either. The car ran with this contaminated gas just fine. It made the plugs dirty. There's some oil on them as well.
The new gas soaked up the old sediment and trashed it but the engine still ran with it. I guess it had enough of what it needed to burn it.

Water and dawn might Break up the sediment in the old tank.
The old tank That was barely used. I keep finding myself fixing things and then the old stuff is out of sight out of mind. Other stuff is a priority. Like now that I have the new tank. The old tank is not worth messing with. Even though I know it is. Because this can happen again and experience of getting old dried up gas out of the tank successfully would be good. Acetone is too expensive and dried out too fast. It also didn't cut the old gas well enough.

Water and dawn on the sending unit took the dried gas off after a soak. If I put the old gas tank in the bathtub with some serious cleaner it should do it. I didn't want to use acid based products or abrasive products so as to not kill the galvanized finish.

I replaced the tank and sending unit with new parts and that made a big difference. The gas is now clean and the car seems to be running well. Probably needs an oil change after 7 year old oil.

I'm thinking 20w50 this time.

The problem was me just not diagnosing it correctly and making assumptions. Not listening to others at points.

I will say that other things slowed progress like the gas tank going bad and the starter going out. It all kind of happened at once. What you get for leaving one sit. This time I will keep it running and just throw new parts at it. It had some vibration on the highway and feels very unstable at 80mph. Could be because it's almost 50 years old.