Well, I gave it a shot. Although I was able to drive my current FH, when I tried to change the chassis, the game crashed. It also happened with my classic FH. I have the heavy-duty mod and when trying to modify the truck, it crashed. I didn't try to buy a new truck, though, will be the next thing I try.
After buying a new truck, I was able to customize it with the parts from the mod. There were even some parts (but not all) from the FH 3rd Generation mod that I could use too.
I must say it's a very nice add-on, well done @Pendragon !
My only nitpick would be the custom paints that I presume came with the mod.
Not sure why the contour is not nicely going around the side panel...