340 Chugging instead of Reving

I put together an EQ headed 360 dirt engine for a local guy. The "cost effective" thing to do is use chevy rockers. Used the Comp 1.6 chevy. After the fact, I learned you need the 1.65 ratio chevys in order to come back to the actual 1.6 of the Magnum. With the 1.6 chevy, I lost lift and couldn't get the geometry correct. No matter what I did with pushrod length.