As stated in the original post, my plane came from the factory with a Gill 243, which does not require a battery box. It was a flooded battery, but was designed with a dam, an aluminum cap and a vent nipple to save the airframe manufacturer from making a box. My plane was not listed in the correct area of Concorde's STC or in the Mooney parts catalog. A call to Mooney was met quickly and efficiently with the factory drawings (the specification that is used with each plane in order to account for changes) which shows the exact point at which Mooney changed the J to the G243. They also supplied an SI that allows the owners of G243 equipped aircraft to change to the Concorde RG24-11M or RG24-15.
I received the contact info from a MS lister and I couldn't have received better service from the factory on an airframe that left 28 years ago. If anyone needs the above info for their J (SN 24-3076 - 24-3218) let me know and I'll send it.