Within the Mahantango formation is a section that is referred to as the "Centerfield coral reef (zone)". This is an area of limy mudstone/shale which has a much more prolific coral population. In Pennsylvania it's most easily studied at some exposures near Stroudsburg. Both exposures can be difficult to get fossils from as they are road cuts and are very close to the edge of the road. Sorry, no pics of the sites as I didn't have my camera with me that day.
As a substitute here is some chunks of rock from the exposures that show the corals in situ. You can see lots of Bryozoans and tabulate corals in cross section.
In the picture below you can see a neat circular feature with "teeth" pointing inwards. I think this is a cross section of a rugose coral.
The main problem with collecting this bed is that the rock is a limy shale and so the fossils don't easily weather out. What you tend to get is pieces and cross sections rather than whole specimens. If I had the proper tools maybe I could prep something out but I haven't seen anything that is worth it yet.