I'll add, the 302's chamber has shrouding issues with larger valves. So you have to make the chambers slightly larger to help that. Not a huge deal, but it will make a measurable difference.
So, you have to port the 302s, and push back the chamebr walls slightly to get them to flow what the Magnums already do, and they are still "limimted" by 1.5 rockers. My point being, in a dollar for dollar build, the Magnums will make more, from less. You're still buying cam, lifters, and pushrods. Complpete heads come with rockers, and you can complain all you want about CHevy designs, but adding screw in Chevy studs and Checy rockers is cheaper than the cheapest 1.5 ratio stamped steel MP shafts and rockers. Plus, the lighter beehive retainers and springs help too. Teh 302s work when you need compression, and when torque is the goal. A drag car, torque is not as important, and the Magnums will make better power for less money. Also, the magnum chamber is slightly better shape too.