RE: 2.4 Conversion
I considered converting my Futaba 9c to 2.4. But after doing some research I found that converting an old radio to 2.4 was not the way for me. The frame rate on the new equipment is usually faster than an old converted transmitter.
You will have to buy 2.4 receivers which ever way you go. So review 2.4 receiver cost before you make your decision.
If you only need the capability of a 6 channel system there are some very good low priced 2.4 systems on the market. The 8 channel system cost a bit more.
You old transmitters will continue to age. Might be time to say good bye. I did and never looked back.