I am by no means an expert at all but I have had a few conversations with Drew (broncitis) concerning frame tie ins since I will be redoing mine. I do not personally see any reason for a bushing but many would disagree. If you have a large enough body lift you can run steel tube (rectangle) on top of the frame straight accross. I am going to do 90* bends with no bushing. be sure to not weld directly to the frame, use a plate against the frame for added strength. my cage also has a floor bar inside behind the front seats. It is more difficult for an entire bar a few feet wide to bust through then 6 small footplates.
Just my .02 cents, hopefully drew will chime in this weekend.
Complete offroad offers nice products if you don't want to fab them up yourself