However, systems marketed as "straight pipe" or those with extremely open designs (like some "true dual" systems with minimal muffling) will generally be among the loudest options. Keep in mind that extremely loud exhausts are often illegal and can result in fines. Also, they can be significantly less enjoyable to drive in for long periods than a more moderately loud system.
To find the loudest options, you'd have to look at manufacturers specializing in high-performance, very loud exhaust systems for small block Chevrolets. You'd probably have to contact them directly or read many reviews to get a sense of relative loudness, as "loudness" is subjective. Be prepared to read lots of conflicting opinions!
Remember to always check local noise ordinances before installing any aftermarket exhaust system.
