Makes sense that there is no FIAT data as the alko was added by Autotrail.
My Cheyenne uses the Fiat Chassis hence why I have a FIAT plate.
As it was Autotrail who fitted the ALKO, it would be their data that would trump the original ALKO spec data, in the same way that the Autotrail numbers replaced the Fiat spec data numbers on mine (reducing 6000 to 4750)
For the weight info I am referring to, have a look at this Autotrail site -
https://www.auto-trail.co.uk/brochures. The closest brochure to your 2001 motorhome is the 2003 brochure. That includes the 2003 Scout on the Alko chassis, both single and tag, plus the Scout on both the Mercedes bases.