I have a 1964 jeep p/u and i was wanted to know if you all think the post-style spring hangers would hold up to offroad abuse, or should i move the springs under the frame?

put the springs under the frame, ive seen a few j-trucks like that and it gives them a good bit of lift

They'll hold up pretty well, at least they've done well on my 75 Wag. Putting the springs under the frame is a relatively easy way to get some lift, but if you plan on doing that, I'd recommend changing to something that is more common, like chevy truck springs.