Hi Wodge,
When I acquired my BJ40 a radio came with it. I have never fitted it and I do not know if it works , although the light came on when I 'tested' it but I didn't have any suitable speakers, so it has sat on a top shelf for years but it fits the slot. That is assuming that the FJ slot is the same as the BJ and I can't think of a reason why they would be different.
But BJs are 24volt and FJs are 12volt but if you think that you could get the necessary conversion done then PM me.
Regards,
Rodger