Many thanks to all who responded to my plea for assistance.  On a 
recheck of all the wiring while the van was running, I picked up the 
cylindrical three-wire connector in the upper left corner of the 
engine compartment, and ...you guessed it...a major hiccup.  

I noticed the connector had been taped with electrical tape by a 
previous P.O. so I unwrapped it and the connections were very loose.  
Closer inspection revealed the looseness was as a result of two 
cracks in opposite sides of the female coupling, hence the tape!

I didn't have a replacement, but a retaped it with a moisture and 
heat resistant tape as a temporary fix.  After an hour and a half of 
various driving, I still have yet to have the engine miss.  I'm 
keeping my fingers crossed that this is the real problem.  

At the same time as the above, I rechecked all other connections, 
pulled them apart and replaced them (several times...looking for 
corrosion) and rechecked all vacuum lines as well.  Also checked the 
connections to the brain, rapped the brainbox with a hammer-handle
a few times with no noticable reaction by the engine.

Once again and with my fingers crossed, thanks for the help.  I'll 
let you know what, if anything, happens next.

Jack Bateman
Oshawa, Ontario
Canada