I think the biggest limiting factors is your GVWR and Engine. I think if you do a conversion and maybe add a pop top or high top you will be maxed out. This doesn't include hauling anything inside, including people. The 4.6 is going struggle more vs say the more common 5.4/6.0 Engines as well.
I think I'm on the lighter side of most of the rigs here, around 7,000 LBS (E350 4x4, Hightop, early stages of a build out, no steel bumper/winch or extra fuel). But a lot of rigs that are fully equipped are 10K+.
I personally would go with a E250/E350 so you have some more wiggle room for your build if you are dropping more $$.
I am no expert by any means, this is just information I've observed from other more experienced members on this board.
2004 E350 RB 5.4L Chateau
4x4 Quigley w/ Fixed High Top