I put a set of the below mufflers on my big block 57, They really are very quite, and they only cost 81.00 each, they are designed for the 1968 caddy with a 472-500 cubic inch engine, so they don't restrick flow and run like a new car.
Manufacturer's Part Number21856
Product LineWalker Quiet-Flow 3 Mufflers
Summit Racing Part NumberWLK-21856
Inlet Diameter (in)2.500 in.
Inlet Quantity One Inlet
Outlet Diameter (in)2.500 in.
Outlet Quantity One Outlet
Muffler Finish Aluminized
Case Length (in)19.000 in.
Overall Length (in)23.000 in.
Thickness (in)4.250 in.
Width (in)9.750 in.
Quantity Sold individually.
Replace your OEM muffler with one of these Walker Quiet-Flow 3 mufflers. They are manufactured from steel and then aluminized for maximum durability. Their turbo-style configuration provides great interior and exterior sound control without decreasing exhaust flow. Available for cars, trucks, and SUVs, these Walker Quiet-Flow 3 mufflers give you the OEM exhaust sound that you have been looking for.