Caster and pinion angle will always be a trade off unless you cut the outer Cs off and rotate them. Not exactly an easy task. I'd probably set the caster to maybe 3*, replace the front driveshaft's forward U-joint if it's not new already (U-joints don't like changes in their operating angles), and call it a day. I do believe caster can be measured off the front diff face. So you should be able to get a close reading from the heads of the diff cover bolts.
Also, tech questions should probably be asked in the tech forum so more guys will see it. :thumbsup: