Year: 1968-70 Description: Smog pump relief valve pressure-setting plug Application: Mustang/Shelby All Jack’s Comments: This blue smog pump pressure-setting plug is correct for the Boss 302, 428 S/CJ & Boss 429 smog pump relief valves. Related Pictures: More Info or Links: Pressure relief valve with this plug is available <here> Shipping US: Free Shipping NON-US: Call or email for an exact shipping quote