Need new mufflers

Ultra Flos,long case.Personal experience.11 to 1 421 Pontiac.Big roller,Big heads.Quiet at idle,and up to 3000.Build ,very similar to 340's build.340,.030" build.Actual 10.8 neasure compression.narrow lobe center Crower roller.256/262@ .050.Nastier than hell ,with Magnaflows.Swapped to short case Ultra-Flo's.Quiet ,with a 3" exhaust,before the axle.