I noticed my PV-183 878 chips get very hot so I started looking for some heatsinks. Over at the zoneminder forums someone pointed to http://www.sidewindercomputers.com for a source of possible heatsinks. I looked there and found http://www.sidewindercomputers.com/enbcbmlowprf.html These looked good and their low profile allows another card to be in an adjacent slot. I may install four more of these same heatsinks on the large controller chip on the PV-183. I'll have to see how hot it gets.
For those wondering... I have no connection to sidewindercomputers.com.