Has anyone here done this conversion? I don't even have my van yet

I had posted a similar question (newer v-6) when I was here awhile ago, but I dont see it now. I drive a 2004 Crown Victoria (TX Sheriff's) and just love the reliability and performance. I would love to put in a 4.6 and trans from a totaled cop car but I think the task would be pretty intense.
My goal with my E-100 Project is reliability and decent mileage.
I had read a thread where someone suggested this, but was wondering if there is a actual member who has done this.
Guy
I am looking for a 68-74 SWB Cargo Van.