99 E350 cargo power windows/locks

[curtis73]

I want to add power windows/locks to my E350 PSD. I found a guy locally parting out his 96 van with power windows. I figured I could bolt the doors on or swap the parts and plug in to some factory harness under the dash.

Then I got to thinking... Normally auto manufacturers use the same wiring harnesses for all the vehicles and just don't use the connectors for options it doesn't have, but this van doesn't have the wiring included for rear speakers or rear air, so I'm curious if it may not have the harness for power door parts either.

Can someone tell me where to look? Is there possibly a piece of the under-dash harness I should scavenge from the donor van?