In 1992, I bought a 1970 FM3 Moulin Rouge (Panther Pink) Plymouth Barracuda at the Ft Worth Texas Police Auction for $475. It would start on ether, but there wasn't any gas in the carb. Cops said I only had 2 days to get it out of the yard, so I rented a Tow Dolly.
Not wanting to drop the drive shaft and spill trans fluid all over the police impound yard, I jacked up the rear axle and speed backed my 1984 AMC Eagle tow car/tow dolly under it. Crash! The jack got knocked over just as the wheels dropped onto the dolly. perfect.
Towing the 23 miles back to my apartment with the car backwards limits me to about 30 mph max. because the idler arm was dead and reverse caster made the front tires tow out about 5 degrees, so it was a long drag home.
Once home, I dropped the tank - Rusty mud in the bottom on the tank and in the fuel lines, and the intank filter looks like it went away at least 10 years earlier.
That's a long story, but here is the math: 1992 - 1970 = 22 years.
2020 - 1978 = 42 years.
In the last 25 years Ethanol has become a thing and rusty mud in old fuel tanks has only become more widespread.
So I ask the next logical question:
When did you put a new fuel tank in it?