I believe they have UV protection included in the mix and it is supposed to retain its color. (It is available in several colors too...)
What are you trying to do to the chassis? Protect it from rust, make it show quality, protect it from scrapes and chips from off roading, etc...
I personally think it would be overkill on the chassis, and you wouldn't want to risk it being sprayed on moving parts like brakes, driveline etc... If you ar simply looking for a clean overall look for the chassis I'd suggest pressure washing it thoroughly to remove ALL contaminates then masking off vital parts and either painting it with chassis black (semi-flat black paint) or rubberized undercoating. This will protect it from rust but can also be easily removed in the future if you want to do any frame mods like installing ladder bars or something like that.
If you are going to show the truck you need to strip it to the bare chassis (remove cab, bed, driveline etc...) and then weld and fill ALL the unneccessary holes and grind them smooth then have it primed and painted to match and finally color sanded and buffed before you carefully reassemble the truck... A lot of work for something that very few will notice and something that will get scratched and chipped if you USE the truck like a diesel should be used!!!