Twenty gallons per tank.
It will have to be of a 88-95 Chevy i believe.
yes
8.9 Quarts for a 1980 Toyota Pickup with a 20R.
yes
In short, YES.
all you can get, depending on the shape and how well it runs
inside frame , drivers side
the two wheel drive version is right about 20 gallons
5 QTS. with a new filter.
No a 1972 Chevy pickup is not the same model as a 1973 Chevy pickup. I believe it goes from 1967-1972, 1973-1980, 1981-1987. Doors will work from 1973-1976, 1977-1987. You would need to find 1972 doors as they are the only ones taht will fit a 1972. 1967-1971 are the same but there is something different about 1972 doors.
My 1980 Blazer has a 16 gallon tank, yours should be similar.
The proper spark plug gap for a 1980 Chevy 350 Pickup is .045, according to spark plug manufacturer (Autolite, Bosch, NGK) specs.