Probably an overstatement, but there are some front end issues for which no adjustment has been provided. For example, wheel camber is typically not adjustable on solid axles - the only "fix" is to bend the axle. Many shops can't (or won't, for liability reasons) do that.
What chassis and front suspension do you have? According to the Built On Freightliner data at FCCC, your 2006 Mandalay has a ZF IFS, but I have no idea why you say it is "modified". I have the ZF and it has been "aligned" by Freightliner Factory Service @ gafney, SC, but I'm not sure just what adjustments are possible. Possibly it is just toe-in that can be set. You might call Freightliner Custom Chassis Customer Service and ask (have the last 6 digits of you chassis VIN handy).
Your 2006 chassis specs can be found here:
Freightliner Custom Chassis Corporation (FCCC)
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL