A line of adaptable utility vans by Ford. Model numbers are typically E-xxx (eg. E250, E350) similar to the F-series (Ford trucks). Higher numbers usually denote a longer van and/or other features, like dual gas tanks, larger engine or custom additions. On eBay I recall seeing a vintage Econoline that had to be from the 1950's, so the line has been around.
Many additions to the van can be easily added by a modest machine shop or possibly as an option from Ford. Some cooler E-series vans I’ve seen were turned into:

-A line truck with cherry picker
-A police truck
-TV news “live on the spot” trucks, with a collapsable twenty foot antenna tower, generators, video equipment and room for a small news crew.

The Econoline chassis itself is also sold as a versatile platform, usually sporting just a front quarter cab (from the front bumper to just behind the front doors). These are turned into things like:

-Busses or large passenger vans
-Small and mid-sized RV’s
-Cargo trucks of all sorts

There's thousands of examples, as Ford's only made a few bajillion Econolines. Those are the best I recall though. I do remember seeing an “offroad” Econoline van that somehow had a drive axle installed up front and was four wheel drive.

These are all trucks at heart, with van bodies. They will ride like a box of rocks if it's empty and going fast over something bumpy. I found myself carrying cargo just to keep the light rear end on the ground. Due to their huge surface area they tend to crab or sail a little bit in heavy winds.

Like any van, these are hard to work on. Seeing those huge engines in tiny compartments is like looking at under the hood of an airplane. The big engine is stashed halfway into the cab, and removing it actually involves tearing out the seats and hoisting it out through the side cargo door. A lot of engine work I did was from within the cab. Due to a body member crossing right over the engine, it might need to be removed to perform trivial top end tasks (valve work, etc). I’ve had lots of transmission problems with my E250, which grew into engine problems. It still runs, but now the poor thing sits unroadworthy until I figure out what to do with it. It was also fraught with electrical and exhaust problems. Like every other vehicle I’ve owned the OEM starter motor wouldn't keep up. However I’ve seen other e-series tearing around with decades over decades of wear on them, but they keep going.

Keeping with the spirit of the White Van Man, I once managed to win a race from work to a Taco Bell over two friends both driving Ford trucks. Victorious was I, operator of big ugly cargo machinery, over newer, smaller fuel injected machines with less weight and about 10 years of design improvements over me. The win wasn’t free however, upon trying to leave the said Taco Bell, part of the ignition system had cooked and I was stuck.

I'd love to get my E250 running again but it needs time and money I just can't give right now. It was sinfully fun to drive; it's sheer mass and footprint demands vehicular repect from any driver who knows what's good them. I've fit anything from dirtbikes to trash heaps in my van, and I happened to get it a year before all the vehicles went all round and goofy looking.