Well the old Chief made the drive fine. Unladen with a BA/10, 3.55's, and 30's (and never quite got around to a full tune up before the drive) I averaged about 20mpg from my house to Moab Utah.
Yeah it's in there - still too short (I was right in guessing that I needed about an inch shortened). When I loaded it up and ran it out it was okay though. About to go unlaod the Jeep and put the long shaft back in for unloaded travel.