i can get watanabes, but they are expensive, heres an example, i used to get rid of 14x6 inch wats to the trueno crowd for 750.00 a set, used,(thats as least 100.00 less than what they usually go for, i had seven sets sold in two hours flat) a set of 16x8s or 9s WILL cost you at least double that in good used shape, thats why just about nobody has them. i sold a pair of 15x8.5 and a set of 10s for 1500.00 each, USED, and thats A55 cheap for the market.
i had a few sets a while back, they sold like hotcakes, but i dont think there is enough market for me to get back into it. have you tried wheelchoice.com? they can any rim dang near, but they will want some big bucks.
on the rear of a 240z, i assume youre gonna run zg flares, i would run a -10 or so so the rim sits a little outward, like a oem snowflake rim or so, that way you could get a 215/40/16 on a 8" in front and a 245/45/16 on a 10" in the back, with the stretch look.