I'm looking at a 1968 280S with 150k miles on it tomorrow. Are there any model specific things I should look for on this car that would raise a red flag?
Look for leak at hydro-pnumatic rear compensator or saging compensator spring.When rear wheels tilt in at the top / \ it is a dead giveaway. Also look at driveshaft flex discs and center bearings would be a good idea.
are a plus. You should have the engine checked out. The rings tend to go at around that mileage, especially the oil control rings. When the engine is warm, open the oil filler cap and listen for the sounds of excessive "blow by" and look for excessive oil vapor coming out of the opening.
Pull the dipstick for the transmission, if fitted with an automatic, and check the condition of the ATF.
Or better yet, if you are not familiar with these cars, have a qualified shop/tech check the car out for you; it will be money well spent, as these cars can be pricey to put right...