Not sure what Ford F450 chassis you have, but most all the ones I've seen can get DRL turned on very easy in the pcm. Some tuner modules will have the ability to turn it off/on, mine does.
Also not sure if you have the Ford pcm in your f450 chassis or the RV up-fitter added their own pcm system.? Or if you have a hid light conversion that does not play well with drl.
A dealer tech that knows his way around the IDS TOOLBOX in 2 minutes can click the mouse once or twice and it will be on, at least on the Ford pcm.
Probably worth asking a Ford tech that knows ids. Many of the service writers will have no clue what you're talking about, need that tech that knows the IDS TOOLBOX. All he has to do is plug into the obd port and he'll know in seconds if it can be done.