Now, I realise I'm a little late, here. But I'll chip in my .02.
I've driven a Chevy Express extended version, and a fairly new Ford F250 (Which, from my understanding, is similar to the Econoline but with a truck on top instead of a van).
The Ford, while it does have its' merits, is tripe. The engine is fairly smooth and quiet, but the transmission is tripe. I find it slow to shift, and coupled with the particular engine infront of it (not sure which one, probably a lower end model) ended up shifting long before the powerband unless you really mat it.
The Express, on the other hand, had both a smooth engine and transmission. It was audible, but in a good way. You could hear what it was doing. The transmission was extremely smooth and had better shift points than the Ford.
As an afterthought, I'd also ask why you didn't consider a pickup with a canopy on it.... Same function as a van, but with a partition.