Bendix-King CDI's require Bendix-King radios to drive them.
... or Garmin. The GNC-250XL is a fairly capable unit for the price, with VFR GPS. It would drive your existing CDI, or you could just use the built in map display if you wanted to free up that hole for something else. It can also take an input from your altitude encoder (for when the satellite constellation gets too small and altitude precision goes down).
I've got one sitting on a shelf, waiting for an appropriate project to come along that needs a radio. Here in the western states, I've given up on VOR. What stations remain in service are often blocked by terrain at altitudes typical for a C-150, so GPS is really the way to go.
They seem to go for around $2200 (eBay and private sellers) to $3200 (avionics shops); with rack, datacard, and antenna.
Installation manual is at
http://www.aeroelectric.com/Installation_Data/Garmin/GNC250XK-GPS156XL_IM.pdf
