Frank, that looks really good!
I'm sorry but I have a "but". The "but" is that the fender pan isn't really strong enough to support a dump bed. The bed needs to be attached to the frame directly and sit on it, then the fenders mounted to the bed. I just assumed you wouldn't use two fender pans. For example, I had to modify the Cozy Cab I got for my 1811 because the fenders flexed too much with just it, and the cab isn't really very heavy. I guess if you don't plan to make it hydraulic, or electric dump, or even dump at all, it would be ok. And as long as they weight limit is no more than a driver would be.... Maybe I'm missing the plan you have, but I really think you need to reconsider your point of attack..... but, it's your build.
Not nit picking or anything, just hate to see you go through all the trouble and it not work as planned. Just trying to save you trouble later.