Yeah, both the 36 and the 40 will work. Only difference is that with the 40 you can't access disc 7,8,9,10 directly. You have to wait until the last song on disc 6 has played, then it will cycle on to disc 7 and so on.
I've got a cdx-T70MX 6 disc MP3 changer including adaptor to go to a MK11 head unit, i suspect it'll be the same to a mk1. How much will you offer me for it?