I think it would be a great idea to drop in those newer duratec 4 cylinders from the last ford ranger. Those engines apparently are very reliable and fuel efficient. Best of all it's a power upgrade from the original econoline engines.
So for those who are interested...
You'd get more...
Power (150hp)
Fuel Economy
Weight Savings
5 Speed Auto
Accessories like AC, Power Steering (Now you can run a brake booster)
The Duratech is a 2.3l All Aluminum fuel injected engine found in the Ford Focus & Ranger from the 2000's era, the Focus is FWD and started out as a 2.0l, the engines have a decent aftermarket, and you can even buy 300hp crate engines if you have the $$$.
To modify you'd need new motor mounts, new trans mount, new driveline, adapting the auto box or mount a new gear selector, wiring for electrical components, electric fans.
You might need a way to convert some of the sensor signals and perhaps the speedo if it's electronic.
In the end you'll have a better balanced van, better fuel economy (20's to 30's) and 50% more power than the stock engine.
And if you don't think an econoline can handle a 4 banger think again, the ranger weighs atleast 3400lb, light by today's standards but the Econoline weighs 2800lb