You really need to trim those bars down to about 500mm at a minimum. The drops on wide bars like that is very likely the cause of your pain. I have relatively broad shoulders and mine are trimmed to 530. I would trim them down more, but with Grip Shift it would push my brake levers in unnaturally far. Once you get your bars trimmed, experiment with different rotation angles on the bar ends. Mine are rotated up a bit more than they are on my road bike and it gives the feel of riding on the brake hoods when I rest my hands on the top of the drops...very comfortable.

As for the conversion, it would likely be very expensive.