[Jrs3800]

When the van does die, Does the speedo still report speed? Or does it drop dead?

You have replaced quite a bit... My next guess would be the PCM... The computer that was used in the 94-95 3800 Powered GM cars and vans was not really known for longevity.. They have a pretty good failure rate.. But they almost never fail completely.. They fail enough to have you chasing your own tail trying to correct for different issues.. I have 3 of those PCM's sitting on the floor right now and all 3 of them have failed... I am on my last and Final 94-95 PCM as we are getting ready to rewire my 95 Bonneville with the 97 OBD2 PCM to avoid the failures..

I can't say this is your problem for sure, but its sounding a lot like it...