I went down this road last fall, switching from 1200#'s to 1500#'s. My advice would be to completely start from scratch with the new bars, head tilt, cam adjustments etc etc.
Remeasure, reweigh, rebuild as if you never had the 1200# bars to begin with.
However, if your tongue weight was 1200 and the setup pulled fine I personally don't see the need to go up.
Mine setup was all over because the spring bars weren't up to the task.
Scale weights are key. My setup 'looked' perfect but the scales told me I was only transferring about 200# of my 1400# tongue weight. The front was at unloaded height with a little rear squat.
You need to pull onto the scale at a truck stop and get weights with the bars up and down, then get unloaded truck weights.