I don't know what problems you would run into with the wrecker body since I've never built either kit but that would make an interesting wrecker. I saw a cab over frieghtliner wrecker this summer, like the AMT White Freightliner, they may not be common but there is at least one.
Diesel doc works on real wreckers and just built the KW wrecker, maybe he will have something to say about it.
Mack Mechanic that is an interesting truck, I've never seen a low rider semi before, do you plan on having it pull a trailer? maybe a car hauler full of custom cars?