FORD Expedition wheels mount on E-250 cargo van?

tire and wheel store.

Wider front than rear? Why would you want that?

Wider than stock is a reasonable question, and I don't know the answer. But the only way a wider wheel on the front would give any benefit at all is if there was Front Wheel Drive, which your Econoline van certainly hasn't got.

weight's upfront: more contact patch with greater weight gives better turn in, grip, and balance.

the expedition's rims go 7.5 wide over the cargo van's ?? 7" cargo van takes 225mm stock expedition goes to ? 265mm

all 16" rims steel only

E250 uses different lug pattern than Expedition, so you'll have to find new wheels or change out the hubs, which I don't recommend.

You do not want wider tires in front than in the rear. Period.

You may want wider tires all around, and I agree completely that there can be benefits, and I'd argue there is no downside at all.

It appears to me that your choice in tires will affect your gearing. You need to consult your tire store for availability of the optiions, and the pricing -- I'm not sure, but I think the tire size you will need is going to be rare. Assuming you have a 225/75x16, and you want a 265, you will need to find an aspect ratio (the second number) of 65 to retain an overall diameter. If you currently have a set of 15s that are 225/75x15, then you can replace them with 265/60x16 and have an overall diameter that is identical for all practical purposes.

You should have plenty of room for a half inch wider rim. You are aware that you are putting on tires that are 40mm wider than what you currently have, right? 40mm is an inch and a half, which is an inch more than the new rims. This will fit okay, but will have a bit of an offroad tire appearance.