I have both a 7.3 and a few 6.0, 7.3 is a great motor but isn't guaranteed trouble free, a bulletproof'd 6.0 is as reliable if not more than the 7.3, we bulletproof'd both of ours at 160 and 190k miles only as preventative measures, both were stock and when tore down they looked perfect. I def know the vans had less issues than the trucks, not sure if this is because the vans were detuned, less hp. Maybe you can find one already done?
Check out powerstrokehelp.com, he's one of the most respected. In one video he lines up all the power strokes from 95 - current 6.7 and talks about issues of each motor. In the end he says a bulletproof 6.0 is the best choice. Just my 2 cents
2005 E350 EB 4x4 6.0 Super Camper HT
2005 E350 RB Passenger 4x4 6.0
1995 Bigfoot 20' Class C 4x4 7.3