Your existing door gap is not perfect then? What are you dealing with now for body mounts (condition, height...) and are you certain that the doors themselves have been adjusted exactly correct?
If so, I'm sure you can modify the rocker slightly to get a better gap. Knowing the occasionally crappy original assembly of these things, I would not be surprised to hear one is not quite right. But generally speaking, the door gaps were surprisingly good from the factory. Hence my question about knowing for sure what is at work here before modifying metal panels.
When you say "on jacks" in your original post, do you mean jacks under the frame, or jacks under the axles? Personally I would put jack-stands under the axles, or leave it on the wheels. Any uneven pressures applied from supporting the frame in non-stock areas could give you trouble unless you are very persnickety in how you set it all up prior to doing the body work.
I always recommend installing new body mount bushings and verifying that the door openings are square before cutting support panels like pillars and rockers out.
Paul
