I got ya, the way you worded it made it sound like they got lucky and put out a dependable engine.
Think about the times, when the 7.3 came out there weren't comparable engines pushing 500 hp and 1000 ft lbs. We're talking gas engines that put out abysmal numbers, some of those trucks pushing 25,000 lbs of weight. I think you're having trouble forgetting about what has come since.
Is there not something in between? I'd say your clean square body there would fall right in between.
As the owner of a 2002 F-350, the Dodge trucks of that era drive as far as acceleration and better with anything more than 10,000 lbs behind them (when the transmission is in one piece), and the Navistar six liters drive better with those same loads. The 7.3 is dependable, and has been for over 375,000 miles now, never leaving me stranded anywhere. Admittedly, it’s had the injectors every 125,000 or so, but that’s due for any engine at that point, and other general PMs. But it is not something that goes anywhere in a hurry, even with a 3” pipe straight back from the turbo. They have a big bore/short stroke and have to build up some rpm before they make much power, it’s just the nature of the beast with that engine.
I don’t like how much power the new trucks put out, it’s wasted, and the wheels spin too easily unloaded. I think 300/650 out of an engine with a long stroke is a good compromise to move the truck & trailer. I really don’t like the fact I can have a GCVWR that requires a class A in a 3/4 or 1 ton now. Sure the truck will move it but if the trailer brakes go it’s game over unless the ground is flat.
As far as appearance? If that square body is clean, runs well, and sounds okay I would take it to any bid. Very few residential customers know the difference between a new truck and an old one. They will notice the difference between a ratty POS and a well kept truck. Commercial guys, especially those with similar vehicles know better, but if they’re any good at business they’ll understand that the end product is what matters and will recognize you take care of your equipment.