Sportsmobile and their updated website
Looks like SMB did a decent job in bringing their site up to date. As far as I know, they are the only "B" upfitter that works with five models of vans (Chevrolet Express, Ford Econoline, Ford Transit, RAM ProMaster, and the Sprinter.)
I am not affiliated with them, but when I stop by, I find their work as good if not better than other RV factories I've toured. The only real place I can compare to is Advanced RV, although this is like apples and oranges in a number of ways, since Advanced RV is generally focused on custom Sprinters and making "B"s, while Sportsmobile customizes/upfits a wide range of vans, be it business vehicles, "B"s, handicapped mobility. I've seen some one-offs which were interesting like a Sprinter with a 10kw Onan generator (yes, 10,000 watts... it was placed with a partition in the back for mobile power at a remote site.)
Price-wise, they are competitive with other "B" makers, although once you go for customizations, the sky is the limit.