I obtained some custom wheels and some large tires from Jim Biondo. Jim upgraded to 300ZX 5 lug rotors up front and Corvette stub axles in the rear to get a better wheel selection as he wanted to change his wheel and tire setup. Plus he now has stronger stub axles in the rear.
The wheels I bought from Jim are 17x8.5 and 17x9 5 spoke light alloy wheels (From WRD, which is no longer in business). The backspacing on the front wheels is 142mm and the backspacing for the rear is 149mm. Note that on the rear, I have Jim's old brake setup that he had these wheel's custom made to fit. The brakes are Arizona Z Car's old rear racing kit with drilled solid discs on aluminum hats. The key is that the hat is 1/2" thick at the stub axle mating flange. So this 149 mm backspacing will be too large if using the stock brake drum by the difference of the thicknesses of the stock drum and the 1/2" thick hat on the Arizona Z car discs.
When I got the wheels and tires, the wheels had 235/45-17 (front) and 255/45-17 (rear) Michelin Pilot SX MXX3 tires. These are the largest wheels and tires that will fit under the stock fenders with coilovers (in 17" anyway). Be aware that if you go to another tire manufacturer or model, the tire sizes for a given designation (i.e., 255/45-17) change enough that the tires could be smaller or larger than desired.
Just before the 2003 International Z Convention (New Hampshire), I bought new tires. The Michelins were old and hard. I had Toyo Proxes RA-1s installed, 235/45-17 front and 255/40-17 rear. I left them with the 6/32 thread depth. The rear tires fit easily, with more room at the fender lip clearance then the Michelins.
The particulars are:
The tire has more clearance inboard than the rim, but a section width
of 10.55" is maximum. The Michelin Pilot MXX3 255/45-17 tires, which
are 10.5" at the widest point. On
Jim's car, these tires rubbed just a bit on a large dip on the outer wheel
house. Note that the top area (~4" on either side of the highest
point) of the rear quarter opening must be "rolled" so that the short horizontal
portion of the fender lip is bent at the outboard edge (still unseen from
outside the car) in a straight up fashion.
Front strut with tire/wheel installed showing clearance at tire, wheel and coilover. Click on image for larger version with dimensions. 1/8" at rim lip to spring, 3/16" from tire (at bead protector) to spring. (Picture taken when the Michelins were on the wheels.) Click on the picture below to see the dimensions.
(click on picture for dimensions)