I just bought a JRC JST-245 also. I don't know if it would work but the software to control the NRD-545 is here:http://www.jrc.co.jp/eng/product/amateurradio/pc545-e.html
I didn't get the rig yet. So I will keep looking. I was looking for the Mic pin out also to wire my Heil Handi mic or buy an adaptor. If you have any info I would appreciate it.