TM wannabe, with tow rig question

I've been salivating over prospective TM ownership for about 2 years; just recently made the jump from a Jayco Eagle 10 to a Hi Lo 1706 (another story for another thread). My TV is a 2000 Dakota Quad Cab 4WD with 4.7 V8, 5-speed manual, 3.92 limited-slip, full factory tow package & heavy duty support group.

Tow rating info I previously gleaned from the TM website listed my rating in the 5900-6000 lbs range. The tow rating info currently available from the website shows a range of about 4900-5100 lbs.

I just recently discovered your forum, and, like many others, am duly impressed with the knowledge & willingness to help in residence here.

Does anybody out there have an answer to this apparent inconsistency??

Gary