Not really. ABS became standard in 03.
Prior to that, it was an option (albeit a common option).
What is rare is a 03+ P71 WITHOUT ABS. They could be ordered without (knocking $50 off the price), as government agencies were exempt from the NHTSB regulation requiring ABS. But it was an incredibly stupid thing to do, so I don't think any departments actually did it...
Member of Northwest Panthers Car Club
2008 P71, Norsea Blue SAP
-Message Center cluster retrofit
-Towncar Signature L heated power seats
-Long overhead console
-Compustar remote start/security