Bill Thayer has recently updated the entry on the Church of Santa Maria in Pantano in his gazetteer of churches in Umbria. The entry has a well-illustrated description of the phases of construction of the church, the decorative blocks and spolia used in the church, the altar inscription, and other things.
Santa Maria in Pantano is right next to the excavations at Vicus ad Martis. In fact, excavators often have drinks and snacks at the bar built into the remains adjacent to the church. So, if you are headed to the Vicus this summer, have a look at Thayer's description; we will spend quite a bit of time around the church. Also, if you've been to Santa Maria in the past, have a look as well; the entry does a good job of explaining things that you might have seen, but not recognized or understood.