^^^You can run whatever
tire size you want...
As long as it fits on the stock wheel
There are no tire size requirements, just wheels.
Here's the rule:
Any type wheel may be used provided it complies with the following:
it is the same width and diameter as standard, and as installed (including wheel spacers if applicable)
it does not have an offsetmore than +/- 0.25 inch from a standard wheel for the car.
The resultant change in track dimensions is allowed.
has a great suggestion for the size.
The shorter gearing is a definite help on the SVTF.
Not only that, you've just effectively lowered your center of gravity by almost 1/2" by running the 40 series.