I figured you diesel guys would know.

I have a 79 Ford big van and would like to put in some diesel power. Are there any smart swaps known other than the Ford? I dont suppose a MB TD would suffice.?? I need the torque and economy. Regards, pardon the digression Steve

I imagine that if someone was determined enough it could probably be done, but the cost would certainly exceed the value of the vehicle. Around here I have seen pretty good looking Ford cargo vans with Power Stroke on tote-the-note lots for $4000. I have seen Ford diesel passenger vans advertised also but have not paid attention to the price.

If torque & economy are what you need (I assume you're planning on towing), the Ford/Navistar engine is the only option I can think of. Unless this is a van that you love so much that you could never abandon it, you would be better off taking Palangi's advice & purchase a used Ford diesel van with a variant of the 7.3L engine (non-turbo, turbo, powerstroke) than doing a conversion.
Just two thoughts (not necessarily facts):
1. TRANSMISSION: If you did this conversion, you would also have to replace the tranny. The auto tranny that Ford has used with their diesels wasn't a good match for the torque of the Navistar, so adapting anything lesser would be unadvisable. That brings me to my second thought.
2. WEIGHT: The Navistar is a big powerplant (it's used in school buses, beer trucks etc.) & adding the compatible tranny would probably also necessitate beefing-up the front-end components.

BTW, if this is a vehicle you love so much that you are determined to proceed with this project, I TOTALLY understand. At times, most of us gearheads ignore practical logic for the love of a vehicle. GOOD LUCK

Nope, definately not a vehicle I can't do without. Thanks for the feedback. Ther's always that hope that one could wave a magic wand and get what you want. I've got a 351 I can drop in and just burn the gas & save the strain. Cheers.