An easy fix might be a replacement u-joint cross that has different bearing dimensions on each end. They should be available fairly readily at a driveline shop. That way you don't need to mess with the pinion yoke and possibly mess up the bearing preload.
This might help you out. Click on the style of u-joint you have and it'll take you to dimensions.
[on edit] Are both trucks the same series? 3200 and 3200? [another edit] They can't be, as the 55.1 series didn't have a 3200.
