I typed 53020006 into my MSN search engine and came up with a couple of web-sites that had info on that casting #. The cehighperformance site listed that casting # as a 93-95 360 Magnum truck block. The mopar1.us site explained about 1992 being a transition year and the first few years of Magnums had a lot of LA features that were eventually phased out. That's why your block had the oil passages through the deck that I noticed by your caliper.
I learned something new today! toolmanmike