Mid eighties they were probably 6.2s. Way more reliable units than the 5.7 GM diesels that debuted in the 70s but very underpowered by today’s standards. The reason they were no good at altitude was that they were naturally aspirated. The turbocharger is the reason modern diesel engines perform better at high altitudes than other engines. It compresses and forces air into the combustion chambers, making more oxygen available to help the fuel burn.
Used to be lots of 6.2s around here, they usually got decent mileage and back then diesel was half the price of gas or less. I’ve driven several and none were anything but slugs, even in Blazers and half ton pickups. Of course I think they were factory rated at around 120 horsepower.
My uncle had a 3/4 ton 4x4 GMC with a 6.2. Going to Colorado elk hunting pulling a trailer nearly eradicated mosquitoes from a tristate area. Talk about smoke! After that gutless wonder ate it’s 7th or 8th starter in 2 years he traded it in for an identical new one but with a 454. I think it was on it’s 4th automatic transmission in 2 years when it set itself on fire and burned down his garage. Pickups sure weren’t what they are now back in the day.
