Differences I know of: master cylinder is slightly smaller (I didn't upgrade mine though and have NO trouble stopping). The rear frame section is slightly shorter, 6" tall instead of 7" IIRC. The bodies sit lower on the frames because of this. The rear leaves are 2.5" instead of 3, the rear axle will likely need to be replaced.
All bets are off on the 08+ E150s. They have 3" wide springs and dana60 rear axles, but also the shorter frame height. If anyone figures it out, let me know.
Thanks for all the kind words, van is driving great and I couldn't be happier. We have several trips planned. Ill keep this thread updated with upgrades and progress.