Greeno,

First thing you should do is try to understand where is it really bent and if so how much? I assume you must be thinking that it is bent based on tire wear or how it drives down the road?...........But I don't know that! Some frames may look bent but in the past someone could have made and adjustment in the spring hangers or elsewhere and perhaps fixed it...........you could do this:
Find a piece of flat , level concrete to park on and if the Jeep is not high enough jack it up and level it..........drop a plum line off of each corner at given known points on the chassis both front and rear.........mark them on the concrete. Draw an X across the points and measure them...........do the same fore and aft along the wheelbase and measure , you should now based on your measurements on the ground get a clearer picture of what is going on with your frame and how straight it is tracking..........
And you cannot use a hydraulic ram and push or pull against the opposite frame rail effectively without that frame rail first being grounded to a known external immovable point.
The correct way to straighten frame rails is to have the chassis clamped near the bend or fixed to a known
external immovable source like a frame straightening fixture which most are drive or push on and then once clamped down push or pull from that external source to the bent member........


