I have 225 60 14" on my 79ZX and have used that size with the stock mag. wheels for 15 years, I can't stick my small finger between the strut and the tire, but I'm on my 3rd set and have never had a problem. They are the same diameter as the original 195 70 14" so there is no speedo change and they look great. The stock wheel is 14x6. If you use the smaller 215 60 14 you will make you car a little faster but your speedo will be off a little. PS: I use 215 60 14 on slotted mag wheels for autocrossing and they lower the car and make it take off like stink on a skunk.
I have them on my car ('82 N/A) and have had no rubbing of any kind. Only problem is there are no "good" tires in that size. All the soft compund tires are made in sizes that won't fit your Z with the stock rims. If this is just a daily driver and you never race it, then don't woory about the compound and go for what looks good, and the 215's look good with the stock six spoke rims. Get the 215x60.