Don't consider bending the float arms. Never heard of that being done. Without a schematic on that vehicle I'm making some assumptions but hopefully I'm close enough to get you started.
Since the problem occurs in both tanks I don't think it's the floats. Problem is something that is common to both tanks.
1, The tank senders are both tied to ground. Make sure that there is a good body ground. On your Camaro it's the ground strap from battery (-) to the right inside fender. Maybe an 80s truck is in the same place.
2, Possibility that the tank selector switch is acting up. Think I would check the gage first.
3, I assume that the sender is the same as your car. That is, it goes from 0 = empty to 90 ohms = full. Using that assumption, use the method Mike describes in the Chevelle thread to see how the gage responds using fixed value resistors in place of the sender input. (inside the attached thread) That should give you an idea if the gage or calibration resistor are the problem.
Perhaps someone else will have a better idea, but best I can do off the top of my head.