187k on my 1995 7.3, original trans (as far as I know)
Regular oil and filter changes w/Rotella and Rev-X oil additive.
I think the PO had the lift pump seals done.
I just replace the original radiator (my experience is these plastic tank radiators don't last more than 20yrs, and I replacing the other hoses, belts and coolant, and it only cost $150 and an additional 30min).
1995 E350 7.3 Diesel, 4x4 high roof camper, UJOR 4" lift