[Good news 1st it's not all bad with the GM "Old" Diesel]

Can you elaborate on [in spite of what you hear GM "old Diesels"] and [not all bad with the GM...]

I don't mean the typical Ford vs. Chevy Polaris vs Honda crap. What are the big ticket items that have given this motor a overall negative rating.

I know the injectors were poorly designed to the extent they are prone to failure. That can be prevented and fixed.

What else?

Under powered - I can deal with that. I'm not pulling cattle here.

What else because if you search on the web on any thing you typically find people are more likely to post problems rather than "My .... is fine"

The engine was designed By DD to produce 135 hp. IdI coupled with 23.1:1 CR, no IC, a cast iron crank and the introduction of crack channels in '97 make for sad stories and tales of highway woe.

If used in the manner intended, the only real design flaws are electronic pump controls on '94 up, and cooling issues on '96 down. There are reliable work arounds available for both.

Block cracking is a concern on some engines after '97, but many have run a ton of miles without a problem. "Ya pays your money, and ya takes your chances"

Also failure of the harmonic balancer can lead to crank failure. 10 years is too old for a balancer and should be replaced.

Where a lot of people (myself included) get into trouble is trying to make the engine into something its not. I will not be a PS, DMax, or Cummins killer. Sorry. Nope. Won't Happen. You can "reliably" expect ~250 RWHP out of a 6.5 with mods. Which compares nicely with a stock Dmax or PSD. Of course, if the owners of other trucks start modding them, you cant ever hope to touch them.

People claim to make more HP, and I won't argue that fact, but anything over that 250 RWHP will dramatically affect service life and usually not for the good, either.

As all things mechanical, the end result is directly affected to your involvment. There are some 250k mile 6.5 that get neglected, but they are rare, and there are some immaculatly maintained 6.5's that pop the big boom at 135k miles, but those are rare too. But if you take a few hours ever other weekend or so, and spend it bonding with your truck, you have greatly increased you chances of joining the 300k club

Cheers!
Tim