Did Ford put 1999 4.6L engines in 1998 Mustang and if so what was the 260 or 225 hp?

No, Ford did not put the 1999 4.6L engine in 1998 Mustangs. The 4.6L engine was used in 1998 Mustangs, but it was a different version than the one used in 1999 models. The horsepower ratings varied slightly depending on the model and specifics, but the 1998 4.6L generally produced around 225 hp, while the 1999 version saw some improvements and often put out around 260 hp. The changes between the 1998 and 1999 4.6L engines account for this difference in power.