I have a 2002 B1500 high top van with 5.9. It was a sick ***** that could not get out of its own way before I pulled it and rebuild it. Step on the gas to pass going 70 and no one was home.
I would skip past the 3.9 and 5.2 and go straight to a 5.9 with the smallest cam hughes offers. That plus the eq heads I installed made it fun to drive and no matter what the speed it will haul the mail when I step on it.
I have a lead foot and use my van to haul some heavy stuff pulling a trailer. If you are just putting around town with yours as a commuter car you may get by with the 5.2, but I would not even consider putting back another 3.9. Just my two cents.