Wow, I just goggled some wheelbarrows and they do not look like I was imagining. I think it would be possible to find one that fit the bill, but it might take some searching.
Also, the boat tail you show would be a lot of work- to be honest, I'm kind of surprised you actually started building it after all this time!
Anyway, now that I have the tonneau and air dam I think I'll be set on the aero front for a while; the truck's mechanicals want some attention!