Re: SB raised roof on a EB van
As far as I know, Ford makes two lengths of van body, both with the same wheelbase. So there is "RB" (regular body) and "EB" (extended body).
Ford does make longer wheelbases in cutaways and the like, and may make custom body lengths for limo bodies or something, but for normal vans, just the RB and EB on the one wheelbase (136" or 138", I forget which it is). The cutaways can have that wheelbase, or one around 156" or one around 176" - but those don't have regular van bodies.
Chevy makes two wheelbase lengths in their van. I'm not as familiar with them, so I don't know if you can get the long body on the regular wheelbase, or if long body and long wheelbase always coincide (they do would be my guess).