EQ heads on LA 318 question

Assuming you are going to keep the 272 .454 cam, I'd get better springs. Off the magnum I'd take the whole thing. Off the heads you should be able to use the rockers, intake valves (have the stems measured and grind faces), maybe retainers, check exhaust valves very close for wear surface finish and good faces, valve covers, head bolts. From the block use or stockpile the cam, lifters (spiders and all), crank, damper, rods and pistons, and all the bolts and hardware.