Good News: Turned out the marker beacon receiver is operational. The indicator bulbs were the problem. Receiver tests plus hardware for the indicator cost $120.
Bad News: The MK 12D nav/com has problems. You can't tune the standby com and the display blanks out when you try to dim the display for night ops. We're gonna have to send it to Narco for repair. Owner has agreed to fix the radio and pay for marker beacons though. So, now we go onto the airframe/engine portion of the pre-buy. More to come in a day or two. Hopefully good news.
Thanks again Carl and Tim for offering up your receivers! Really appreciate it!