The OEM NA TB is 68mm.
The 74mm comes from a MB model that has a larger displacement engine, or from a Crossfire SRT6.
Yes, you can still utilize a CAI, the outside dimensions of the 68mm and the 74mm are the same.
To really get the bang for your bucks, you need to add in a Eurocharged tune when all is said and done.
( the EC tune is on sale just now at $300 )

NOTE: I have had a NW CAI, 74mm TB and EC tune on mine for about 4 years now.