Welcome. 7.3L's can be a challenge to find, but they're out there.
6.0's are great with some modifications, 7.3's will probably have more miles (due to their age), and V10's have a lot going for them. If you're not towing, a 5.4L works for many people. I wouldn't let the engine limit your choices if the right van comes along.
SMB-less as of 02/04/2012. Our savings account is richer, but our adventures are poorer.