New York - Sirius Satellite Radio on Tuesday announced an agreement with automaker Lincoln, to make Sirius radios standard equipment on select 2008 model year vehicles. A six-month pre-paid Sirius subscription will be included in the price of the Lincoln MKZ, Lincoln MKX, Lincoln Navigator, Lincoln Navigator L and Lincoln Mark LT. Sirius said nearly 600,000 Ford, Lincoln and Mercury vehicles have already shipped with factory-installed Sirius radios.