I need to make sure I'm reading this correctly. I have +3° camber, and +1° caster on my drivers side. If I read the directions, that puts me at FG/Y. Will that straighten out the camber? Or if I have +3, do do I need to go backwards on the chart to +1° camber and follow that down to 0° caster which puts me at L/Z.

 

Use your head, not that chart
You need to know what shim is in there first, then you can decide what cam you need to get it back into spec
You have a lift kit on the truck or what?
Have you measured the ride height to come up with your needed camber number?
On a stock ride height truck, you are looking for roughly .75 camber and 3.5 caster with a small split for the crown of the road
I take it your truck is a 1989 F150? Most of those came with a zero cam in them
You can take the big nut off and wire brush the top of the cam to read it's degree
The biggest cam Ford makes is 1.5 degree but there are aftermarket cams that will go 2.5 degrees

 

Doing alignments is easy really, if you understand the basics.
Ford et al. teach the basics in such a way as to be understandable.
The procedure for an older Crown Vic for instance requires you to put J hooks on the upper a arms and adjust by "counting the flats"
Meaning the nuts on the adjusters have 6 flats, and you move the nut say 7 flats, to go from one camber caster number to another. (and yes, they have charts)
Nobody does that in the field, you take a big pry bar and move the a arm some, and re measure
Same as your truck, you see what cam is in there, and install the required cam to get you where you need.