PROS : They are ****in' sweet
Seriously though, the LT1 in Caprice's and cop cars have iron heads. The ones in the camaros are aluminum, so the camaro ones are slightly more desirable. LT1's make good power and are a good engine. In recent years the 5.3's have become more popular.
Price, I would say for a complete (harness, intake, etc..) "iron head" LT1 market price would be about $800. $500 would start to be the line for a "good deal".
For reference I picked up my "aluminum head" complete with tranny for $600 5 years ago. It has been sitting next to my chevelle making "vroom" noises ever since...