I was always told the pinion angle should be within 2.5 degrees of parallel. If they make a 3 degree shim, that is probably the way I’d go.
And let me guess, you’ve got an XJ rear end in your Eagle? That’s what’s in mine and despite everything I read about the pinion angle being correct, it’s not.
I have probably the same amount of travel in the driveshaft, but no vibration, even at 75. Maybe it has something to do with the wheel base, but I’ll let someone who’s smarter than me chip in for that.