This is straight from the SCCA Club Racing site. Granted it is not the rules. I guess it is wrong - I looked in their database and you are correct.

SCCA Web site:
IMPROVED TOURING...
A VERY GOOD PLACE TO START
Arguably, SCCA's most popular entry-level production-based category, Improved Touring (IT) is comprised of 4- and 6-cylinder and rotary-powered automobiles featuring limited modifications. These cars do not compete on a National level, but is probably the most popular Regional-only classification. Improved Touring is separated into four classes: Improved Touring - S (ITS), Improved Touring - A (ITA), Improved Touring - B (IT, and Improved Touring - C (ITC). The vast majority of cars in this class are former Showroom Stock cars at least five model years old (but no older than the 1968 year model). Engines and transmissions are blueprinted stock assemblies with the majority of modifications centered on suspension improvements, making IT particularly attractive to the budget-minded racer. In addition, with over 250 different classified car models and a very stable rules structure, Improved Touring is capable of suiting virtually any racing budget.

Cheers,
jagman4