First off I do agree 7.3 PSD all the way!
All, except the turbo will do 90+. (Doesn't happen often)
You sure you don't mean non-turbo??? A non-turbo 7.3 is a dog compared to the Turbo PSD. In the van even with the turbo you have the non-intercooled version which cuts back on power numbers a little but it's still has better numbers.
Our last two units will only do 93, (compared with 113 on the older units), but they have all the power needed to haul 10,000 lbs around like a sports car.
If they only do 93??? They must have a governor or rev-limiter or something. I know my truck w/o a chip will only go to 99 and then de-fuel. Maybe yours have some other restriction?.
As far as the 6.0 being less powerful than a non-turbo 7.3 there has to be some explanation or perhaps you have much different configuration than comes in the pickups or "civilian" vans. All these engines come in different HP/torque ratings from Navistar maybe for your application it is setup differently. You did mention that these are custom ordered with diff. transmissions, rearends etc. Maybe they offer the more modestly tuned engines to increase longevity in these brutal commercial applications???
So, I don't think the comparisons in a E-350 ambulance will equate to the pickup truck numbers and real world performance.
The trucks he is going to look at will either be the Turbo PSD at 250/525 and the 6.0 at 320/560. Either of which is going to be a HUGE upgrade in power over the non-turbo you mentioned.
P.S.
I also have PSD and I too agree that it is great and have no desire to run out and get a 6.0 I can put in a $300 chip or use a programmer and safely run the same HP/torque numbers without the need to spend another 40K. /forums/images/graemlins/blush.gif Now the new interior and tranny is nice though /forums/images/graemlins/grin.gif