I have read on another forum (RV.net) that towing a TJ on a tow dolly will damage either the transfer case (if in Neutral) or the Transmission (if in 2H), but I cannot comment on first-hand experience.
However, I did want to mention that '05 and '06 TJ's do not put on miles while being towed (when the ignition is off). So the seller's comments that "It has been towed thousands of those miles on a tow dolly" is not likely to be true. Any towing miles will be in addition to the 37k on the odometer.
2006 Black Unlimited 6-speed, Rubicon Express 4.5" Long Arm Kit