The suspensions & brakes are identical between the ITC & ITA models i.e. CRX = CRX Si and Civic = Civic Si. The main difference is that you can run a 1" wider rim in ITA. The ITA CRX's can run 13" or 14" rims, but I believe the Civic Si can only run 13" since they never came with 14". So all of the 'go fast' suspension & brake parts are equally available and interchangeable.
The main differences are the cylinder head and the fuel injection system.
The ITC cars use the prechamber CVCC head, which gets good gas mileage and produces less pollution but, really sucks when it comes to tuning i.e. if you run too much spark advance, you eat spark plugs. The ITC can run the stock or spec alternate downdraft carb.
The ITA cars get a much better head design without the CVCC prechamber. They can tolerate more spark advance. The fuel injection is much better than the carb'd car. You have to watch out for fuel starvation on the ITA version. Either run a full tank (if stock) or design a surge tank if converted to a fuel cell. The ITC cars can just about run on fumes and still pick up fuel so you can run lighter fuel loads.
That said, the ITA cars will never be anywhere near as fast as a late model CRX Si. The late model cars make so much more horsepower and have much better suspensions.
If you want a car that is really fun to drive, build either one.
If you want to be a front runner, build a carb'd ITC car.
If you build the ITA car, you can always convert to a Limited Prep G-Production car down the road if you like to tinker. I plan on converting my ITC to G-prod next year and upgrading to the Si head & FI set up.
Yes I know I won't be competetive, but the though of driving my current car which is a really fun car in ITC trim, with 20-25 more horsepower from the Si setup and a little more cam should be even more fun! Plus the car is bullit proof!
You might want to consider a later model Civic for ITC, such as the type that Tracey Nine drove to an ARRC win last year. I think the development curve is starting to flatten out on the older cars. I think you'll see the newer Honda 'C' cars getting much faster in the next few years as the development continues.
