try to make space between genny and differential for a sway bar - just in case you want to add one- my pleasure way has the genny too close.
also suggest a petcock on the fuel line- I can reach mine in front of LR tire- also add a filter and external pump- much easier to service if these are outside the box.
here is a pic I happen to have of a diagonal brace on the driver side taken from rear of van ( 2005 express 3500):
https://photos.app.goo.gl/T6Pzo853BrHhYzb47