do not postion the jack on either end . must so on unlevel ground put your jack in frount of ether framerail. and man my buddy got a broken hand from a hi lift jack but they are the best enjoy later chris
Immediately after I bought my FJ60 I replaced my bent OEM bumpers with aftermarket ones from CCOT. I don't remember is the OEM is thicker or not. That being said...you might be OK on the rear if you lift near where the frame/bumper support is. On the front, the jack needs to be further outboard to lift just one side of the truck. The front frame rails are close enought together that you'll lift both tires off the ground if you lift under one of the rails. My front bumper wasn't strong enough to be used by itself.
I made some bumper perches from channel stock that bolted to the rear frame between the frame and the tow hook. I had to cut notches in the rear bumper, though. For the front I stiffened it up by bolting a piece of 3 x 1.5 inch channel underneath the bumper. That seemed to work OK. see this post.