late-model 4cyl in an old econoline?
 

Welcome to FTE.

Sure, you can do that. You might save some gas, but it would be hard to save money doing it.

You have a shop, welder, donor car?

And:

https://www.scs-delta.co.uk/ford-ecoboost-ecu

A better option would be a 4bt Cummins. Its cheaper, easier to swap since its all mechanical and only takes 2 wires to make it run, easy to find parts for, and it will have plenty of torque to pull that van and can achieve 25 MPG or higher depending on the weight of the van.

If someone was going to the diesel route, what are the guidelines for transmissions and rear end ratios since the high limit for a diesel is around 2500 RPM?

Rearend ratios for diesels are the same as gas engines. My 99 SD F250's rear is 3.73. And speakin of 4 bangers, I drove a Dodge Ram van last year to Kansas, coulda sworn it had a hemi in it. It wasn't. It was a big 4 banger that if doubled added up to a 500+ inch V8. And got 17 mpg on the highway doin 75 . If it weren't so butt ugly, I'd a thought about buyin one.

A Diesel is better off with a higher geared rear like 3.55 or 3.73 and an overdrive transmission since the operate at a lower rpm. What transmission and gear ratio do you have now?

An E200 is either going to be a Ford 303 3 on the tree, or a C4 automatic.

Axle ratio would be 3.50 or higher numerically, even a 4.10 would be possible.

Even with a balance shaft, aren't those motors a real shaker? Especially when it's at your elbow?

If you are running a C4 I would recommend 3.07 gears and a low stall converter if you are going to use a diesel engine. The old Cummins 4bt and 6bt are pretty smooth running, they only shake allot on shutdown.

A C4 will NEVER hold up to a Diesel. The HD C4 didn't hold up to a 302. I had a 69 Club Wagon for ten years and had the C4 rebuilt 5 times. Every two years you could bank on it takin a dump.

I agree that it's not the best choice for a diesel but they can be built to handle quite a bit.

This is one of the problems with that conversion. OP is pretty much stuck with an automatic due to the "way back" placement of the transmission in that model van.

A good built E4OD/4R100 transmission with a stand alone PCS controller would probably be the best option but not cheap.

He'd do better with a C6. The stuff done to C4's are geared towards drag race applications, not everyday use. The C6's were used behind the 7.3's

After an extensive 45 second search and review, it seems the 4BT came with a GM TH400 in a lot of Chev chassis trucks. In Fords, he says, mostly manual transmissions.

So, a 4BT to GM auto would be easy, but OP would probably have to step up to a later, stronger, electronically controlled transmission.

And then there is Dodge. A 47RH/RE from behind a 6BT in a Dodge pickup would work.

Nowhere do I find the words "cheap", "easy", "inexpensive", or anything else leading me to believe that the OP would be well served going down any of these roads.

C6: Adapter Plate