Closest you're gonna get to the sound of a classic is an O/R H and a pair of chambered Flowmasters. These 2v motors don't really sound anything like a push rod does. Performance wise there isn't really any substantial difference in power between the various mid-pipes and mufflers.
Sold - Black 2000 Mustang GT, gone but definitely not forgotten
- Silver 2007 Corvette
Current - DHG 2001 Bullitt