there’s also this crazzzzy acid (really not sure what type it is) my buddy uses on his 86 and it just literally disintegrates all of the rust and leaves you with fresh metal behind. it’s in a bottle and you just use a brush to swab it on the surface you want treated once you’ve wire wheeled some of the initial rust off. it requires those heavy duty lab gloves and apron…i really don’t know where he got it from but that stuff definitely works. just letting you know that there is something like that out there.
if not sandblast, i would go with that and por15 after.