My 6.0 has been as reliable as the 7.3 and both have had the same maintenance costs... the 6.0 got a bad rap with all the bro trucks, tuning and pull head studs. Vans have been de-tuned and if it's been bullet proofed it's as solid as any 7.3 van.
I sold my 7.3 RB to get a 6.0 EB, I could have easily put the money into my 7.3 with converting to 4x4 and what not but wanted the extra room and found my current van which I'm happy with... everyone knows to expect the extra maintenance with a Diesel.
I think you should consider the 6.0 but if you do go with putting a CCV pop top on and keeping your current rig I promise I'll do a good job with your pop top
.