Dual exhausts on 75 Scamp 318

After referring to my new-to-me 1975 Chassis Service Manual, I discovered that 1975 360's with dual exhaust had NO cat converters installed - only an air pump for major emissions equip. Must be a cleaner engine that the 318. SO, does anybody know how similar the 360 and 318 headers are for 1975's?? Will the 360 H pipe fit the 318?? That will tell me if I can use the 360 dual setup.