I would like to understand how to evaluate a ballast and determine if it is suitable for a T12 8 foot flourescent bulb. What is the process / questions to ask?
I have several known good working pulls and new ballasts that were inherited:
The common 8' fluorescent tube is an F96T12 and has 1/4" steel nubs on both ends of the tube. They take 1 wire per tube end.
You need to look on the ballast at the list of tubes it supports. If that tube is not on it, then it won't work.
Also, if the ballast diagram calls for 2 wires per lamp end, it cannot support F96T8 which obviously has only 1 wire. So most of your stash can be immediately excluded.
Also be aware that most ballasts for 8' fluorescents are not the same "form factor" (package mounting bolt positions) as 4' tubes.