Its episode 69 and I didn't even make any jokes about the number in the podcast, getting soft in my old age, I guess. This episode is part two of the chapter Paganism in Christianity from TW Doane's Bible Myths and Their Parallels in Other Religions. Deads tree editions of the book are available here: http://amzn.to/1gr5pwK
This episode is a bit shorter than normal, but I think that with the way things are going, this chapter is going to be at least a 4 parter, if not a 5 parter. And if you think that's rough, remember, it's taking me about 4 hours to edit each of these episodes, and I have to listen to them over and over while I'm doing it.
I couldn't find anything on the Church of St. Martins that Doane mentions, but I did find things on the other churches which were built from former pagan temples.
Temple of Apollo, now the Basilica of Saint Apollinare
The Pantheon, originally dedicated to Jupiter.
The Church of Reparata, former pagan temple.