Well, when I first read your post, I saw "2003." I was going to warn you about the injectors, until I read on with your post.
270,000 miles for an '03??? I would try to find something better. Yeah, on the old diesels that don't have the DPF systems that actually accelerate polutants within the crank case, you don't have to worry much. But that 270,000 mile thing is still high for the price. I'd try to get it for under $7,500 if it were me. Otherwise, I'd search for a newer model with less miles and bit higher in price. Again, that's just me.
Does the seller have the actual mechanic's receipt indicating the mileage on the truck at the time the injectors were replaced? Many of the '03, 04 and '05 Duramax's had to have the injectors replaced at around 100,000 miles. If that's the case, the existing injectors already have 170,000 on them. I'm not sure, but did GM replace those faulty injectors with the exact same ones, or were they new and improved injectors, thus eliminating the original problem to begin with?
How's the transmission? Without actually taking it to a mechanic that specializes in '03 GM trannys (don't recall if that's an Allison that year), I'd be really leary.
Also, hows the water pump and coolant system for that matter? I'd want the core scoped too if it were me. I'd also have the axle looked at, although that's pretty bullet proof.
What was the truck used for primarily? Towing??? Does the seller have all his receipts for all the routine oil changes? I doubt it, but it doesn't hurt to ask.
These are just questions you have to find the answers to when buying a vehicle with so many miles on it already. Yes, diesels tend to live longer lives in terms of mileage, but I'd still be questioning EVERYTHING. You gotta ask yourself, how long do you want to own this truck?
