Nothing special about the original 3 speed transmitter, apart from Acoms including a shift gate in the box.
The new 'official' 3 speed transmitter is the Futaba 4VWD, but all it is is a rebdaged 27mhz version of the Skysport 4 with a plastic shift gate included in the box.
Much better is to choose whatever 4 channel radio you want and get a shift gate from
Bruiser Builder.
If you prefer steerwheel then get a radio with a third proportional channel and replace the third channel potentiometer with a 3 position switch.
Looks like it just needs cleaning up, not much needed on the chassis assuming the gearbox works fine. Bodies are no longer the expensive option it was thanks to the rerelease ones. Just as long as you don't need to replace the tyres it's an easy restore.