Why the '89 cut-off? Anyway, I wouldn't trade my engine for a 7.3 Powerstroke. I have experience with one--a 2003--and I prefer mine. Better fuel economy and faster acceleration with a load. The truck I used was a 7.3/6-speed but it wouldn't give you any fuel unless the cruise was set. I did 3 long trips with it--one with a '65 Mustang on my 2,100# trailer from New York to Indiana; one from Delaware with an '87 K30 Chevy on the same trailer and one to Wellsville, Ohio and back with my 4,200# B2 on the same trailer. It cheats you on power while accelerating. You cannot maintain speed on hills without downshifting. But if you thumb the cruise button, you can make the hills without downshifting.
The 6.2 with a Banks turbo in my truck is about 250hp/450ft#, but you have it all the time. It will easily kick the '03 6-speeds butt accelerating and it holds the hills fine. It's not as capable of the power that the 7.3 Powerstroke is with a chip and such, but it doesn't need to be. When my dad drove a semi, he had 275hp and an 80,000# truck. My 185hp, 18,000# schoolbus does 70mph all day long. My 250hp, 6,000# pickup pulls my 10,000# loaded trailer without trouble. If I blow it up, I have two more engines for it. If I blow those up, I'll install a 5.9 Cummins. But it's been 6 years that I've had this truck, and 8 years that I've had 6.2s--same turbocharger on both trucks. And it's a daily driver as well. I'm not anticipating the Cummins swap.
And I love the V8 sound. On my bus I can't hear the buzz. But Cummins pickups bother me. I like the full sound of a V8.