Hank57 & Lantly, thanks for the imput. I told DW over a year ago that the Transmission would probably be the first major repair. I'm thinking about spending a day at John Woods' shop on our way from Phoenix to LA to visit family at Christmas time. It seems reasonable to do a rebuild on my time rather than wait for it to go out and then have no choices.
"The weak links in a 7.3 supposedly are the air intake and the exhaust systems which tend to leak and hurt performance. Look for carbon/soot build up at the Y pipe where it attaches and where the bellows are. They supposedly used a brittle donut to seal and it deteriorates with time and the bellows leak. I just saw an ad for a new turbine wheel which is lighter and more efficient for the 7.3 in DP for this month."
I have an appointment with my diesel mechanic Tuesday for some routine work and will discuss this with him, as I have no real idea what all that is about.
Apologies to the OP for HJing his post.