Asking which car would be best for ITA is like which girl would be best for... well anyway, they'll all work it's just a matter of what you like. The rules have made all the cars relatively equal for the most part as there are cars that excel in one area but are a lacking in another. You need to know what your rationale is for picking a car. Personal choice, what the internet said, what you read in Grassroots all need to be considered along with the financial end of things. How fast you want to get on the track and what kind of support you can receive throughout the racing season.

If something breaks at the track consider what other cars might be at the track that might loan/rent/sell you a trans or fender etc. Some of the older hard to find cars would make this, in my opinion, harder to do.

Some people like to get unique car that present a challenge to them to make them work. Others just want to get in and drive. While building a Monza, finding a good donor may present a challenge in itself. On the other hand, you could drop a cage and some shocks/springs/sways in a bone stock Miata and have a fairly capable ITA car that can be a building block as you and your skills develop. There's no digs at anyone at what they drive, I'm just presenting the easy button. IF I didn't buy an old spec Miata, I would've bought looked for a BMW E30. Option C would have been a CRX/Integra.

It all a matter of personal choice and economics as to what is the best ITA car to drive. I say Miata, others may have different opinions and all are valid considering the equality among the class.

Good luck