I have Mustang 1997-08-21 build date, and first I bought 170 liter/hr. fuel flow pump for 1998 Mustang from Ford Racing (I have it for sale ). Now I have Vortech and Focus SVT fuel Pump and it works very good. I read a lot post in many forums and there doesn't exist 1998 Mustang with returnless system. 1998 model has different fuel pump andbasket. If you want, you can send me PM with your Vin number and I can check which pump do you have 96-97 or 98.
Svt Focus fits with no modifications, you only need pump, without basket