As an aside, at moderate fuel and boost settings, the turbo 6.5L had better reliability than the NA 6.2 and 6.5. Why? Yes, some of that was improvements in the engine structure but equally it was that the turbo engine produced adequate power. The NA engine is a slug, so to get the performance, you have to flog it everywhere, all the time. This was more an issue with people that worked their trucks hard, namely the 3/4 and 1-ton crowd that towed near at or over their GCVWR. I put a Banks kit on my '83 Blazer 6.2 and it was wondrous. No reliability issues at all during my ownership.
At about 160K miles, I rebuilt the engine and bored it 0.030." Add a bunch of performance stuff to it as well, which raised boost and fuel rates and power output. Still fine under my ownership, but the guy I sold it to blew it up. He bragged about doing 90 mph in it hour after hour. Thing is, it had a 700R4 and 4.88 gears with 35 inch tires then. The 700R4 is a TV controlled trans, so basically with lots of pedal applied, it never shifts up into overdrive. You can do the math but at the reported 90 mph in direct, the engine was spinning at upwards of 4,000 rpm. Hour after hour. Unfortunately, I had the pump guy set my governor up to about 4300... IIRC. That was mainly to facilitate some dyno testing, which consists of short runs at speed only (and then only to 4K rpm fer Pete's sake) Driving like that was not something I anticipated doing. But I have digressed.