1996 bonney, 145k ran 100% when given to a relative 3 years ago. It sat in the driveway, started intermittently, Sta-bil was added to the gas. It eventually ran down to empty.

Added 5 gallons of fresh gas, plus some Sea-foam, and fuel injector cleaner. Now runs great for 3-5 minutes, then wants to die. Jiggling the gas pedal can keep it from dying. Sometimes it will shoot up to 4k rpm. Sometimes it will smooth itself out and idle indefinitely. When it dies, or is shut off, it will NOT re-start. Crank crank crank, no sputtering what so ever.

Fuel filter was done around 110k, and a new fuel pump around 100k. If its the fuel pump, is there a way to do it without dropping the tank?

I'd change the filter automatically. It'* time. Then check pressure, if low or it leaks down quickly (under 10 min) the pump should be done.

If pressure etc are good, maybe something else is warming up and failing like a sensor. We've seen similar behavior from crank sensors..although they are not usually this consistent.

On the tank..I feel your pain. I joke that mine is held in with velcro... You have to drop it.