The 604 manifold has been blasted and some kind of coating on it seams to be very tuff stuff. Has choke tube installed like the 584 manifold. Has two heil coils installed overall it's a vary nice manifold. The 583 is still needing blasted and coated but a pretty nice manifold. Both a are 21/2 outlets. Selling as is no warranties ships to lower 48 only. Payment due within 48 hours of end of action.thanks God bless.