I just went through this same experience with my 1979 GMC that had been parked since 1991. I suggest using the mechanical fuel pump to pump the old gas out into a container via a rubber hose. I would go down to O'reilly's and buy a small preformed fuel/brake line to thread into the carb. They sell the ends that are only a couple of inches long and not very expensive.
Here is what I did with mine. I used a hand powered transfer hose, aka siphon hose, hooked to a container of gas and the other end attached to the new gas line. I had my son hit the starter while I stood with a can of starting fluid to help it start. My neighbor stood holding the hand pump. He regulated the gas flow to the carb simply by pushing the handle down. It was very simple and worked very well.
The nice thing about doing it this way is that you can look at the exhaust and see if it smokes. You are running fresh gas through the engine and if there is any problems internally, it will smoke. You want to check the oil when you are done to see if there is any antifreeze in it. I hope this helps.
BTW- I still had to drop the gas tank and replace it along with a new sending unit and all of the related rubber hoses.
1
