Go to the Stewart Components web site and buy from them. They are worth every penny.
Cylinder bore from 170 degree coolant is a non factor. The difference in cylinder growth in 20 degrees is not enough to cause wear.
170 makes more power but takes a different tune up. If you are into emissions, catalytic converters and junk like that, run the 195. If you want horsepower, run the 170 and tune it for it. If you live in a temperate climate you may be able to use a 160. Or, if you only drive in warmer temps you can use it. I drive year around and in sub freezing weather so 170 is about as low as I can go and still get an effective heater.
