A couple of years ago I scored (dirt cheap) a Crown Victoria oil pan with stock oil pump screen on Ebay. I've had it put away the whole time. I took the parts out of our storage room to look at the stock Ford 351W oil pump screen today. It has oil dried in the screen, but at the same time I felt the opening of the screen to be a bit small for use in a Mustang swap since it is a performance application. The stock oil pump screen is part number E3AE-6622-BA and the one I purchased today from Advance Auto Parts is 83-S1 from Melling Engine Parts for $18.28. Autozone has the same part number, but for $24.99. NAPA has the Clevite brand COP6011571 for $28.99. The Melling (and Clevite) oil screen opening is considerably larger. I have never seen the oil pump screen that comes from Ford Racing Performance Products Foxbody 351W swap kit so I can't compare it. I would say that if it is the same as a regular stock oil screen I'd pass on it in favor of the Melling or Clevite pieces. I wouldn't even bother with Dremeling a stock oil pump screen. My $.02.
Another part number to cross reference with is Sealed Power 224-12143