When ever I look up cylinder heads for the sbm it always includes the 340 and 360's. A mild 318 doesn't need 170cc intake runner's, a 318 that's built for the street usually focuses on low to midrange torque. A cylinder head that had more like a 150cc to 160cc intake runner size would be better for low to midrange torque. Not everyone needs 180cc intake runner's and 2.02 valves. AFR has a 165cc intake runner sized cylinder head specifically for the 289 302. Some guys use mopars 302 swirl port heads and that's fine