[99Roadster]

I have a couple of questions I would like answered if possible.

First concerning using the spare tire...I currently have Pirelli tires on my P-car
Front: 225/40R18 Diameter - 25.1
Rear: 265/35R18 Diameter - 25.3
Spare tire: 105/95R17 Diameter - 24.9

So if I have a flat tire on a rear tire is it ok to use the spare or is the diameter difference going to screw with my tiptronic transmission ?....I seen someone say something about taking off the rear tire then taking off a front tire and putting it on the rear then put the spare on the front.

And I run NGK plugs in everything I own and I want to convert my 99 base 2.5L over to NGK's....So can someone confirm that it would be a NGK BKR6EK (2288) ?