Car tips.

[Baron Doune]

Ok going to start working on the old van.  2000 Ford E150. 5.8 liter V8.

Has 260K miles.  Radio still works.

Runs fine in park but  misses like crazy in drive.  No check engine light.

Each plug wire has an electronic thingy on it (coil? not sure).  Really expensive to replace all the wires.

Any thoughts? 

I've got the tools, I've done head gaskets before but I'll be damned if I can diagnose what's wrong.

[Hoowil]

That van should have individual coils over each spark plug, so that sounds right. If you have the equipment, check you fuel pressure. An idle takes alot less fuel, so if the pressure is low it'll run like crap pretty much whenever there is any kind of load on the engine.
Does the check engine light work? It should come on for a test cylce whenever the key is first turned on. Sometimes when people say the light isn't on, it really doesn't work.
Start with the basics. Fuel, air and spark. Air is rarely an issue. Fuel pressure I already mentioned. Check your spark plugs. See if any of look worn, wet, damaged, or just a different color than the others. This can help narrow down which cylinder. Also, verify that the spark plugs are the right ones for the engine. Sometimes the difference between platinum, copper core, and double platinum can be astounding. Check you local parts supplier for what is an OE recommended plug. Manufacturer shouldn't matter too much on a ford, but plug number and type is important. There should be a short wire, or boot that goes from each coil to the plug, with a long spring inside. Check these for cracks, or little white circles. These can be weak points where the spark is going through the boot and into the head, instead of the plug.
Those would be my first suggestions. Let me know how it goes, and I'll think of what to try next.