Need new Cats. Don't have to pass emissions, does anyone know what size I need or a brand to pick? I was looking on ebay but for a 1998 Z28 ls1 they had more then one size. Also I want high flow ones or something with more power but as far as these brands go I have no idea whats good? Thanks

Stock heads and I believe stock exhaust outside my cutout

 

Random Technology makes a good high flow cat