Have the seller check the VIN tag for the date of manufactor if it's 12/97 or earlier it's a 12 valve for sure. It may still be after that I'm not sure but before 1/98 It is a 12 valve I just went though this buying a 98 quad cab from WY. this week. Also as long as it's original on the doors where it says Ram 2500 under that on a 12 Valve it says "Cummins Turbo Diesel" on the 24 Valve it says "24 valve Cummins Turbo Diesel" good luck