I know the new mustangs are returnless but not sure if 98 is. I should know because I own one. Never the less if it worked on the 97 it will work on the 98 motor. The block is the same and does not care what the fuel system is only what computer you have.ok, i know the engine is the same, but i beleive the 96-97 had a return style fuel system but the 98 and later had a returnless fuel style system, and was wondering what was needed, if anything,for the swap, please correct me if i'm wrong :headscratch: