[MDFarms]

Originally Posted by pjmoreland

The filler neck on 67-70 tanks is 2" in diameter, whereas the filler neck for 71-72 tanks is 1-1/2". Here's a screenshot from gmcpauls.com.

https://gmcpauls.com/fuel_tank_&_related.htm

Mine is a 72 so what did you use? So is my filler hole in truck body same size and just bigger grommet? Never realized there was a difference.