360 Magnum building on an existing bottom end

On a budget....Get the cam reground by Oregon Cam Grinders. Give him your goals. Inspect, clean and Re-use lifters. CR is more like 9.2:1 with thin head gasket and stock pistons. Inspect bearings. As the Professor said.....Heads are a question mark. Home port factory heads if in good condition (no cracks) but will have smaller valves. Use Hughes 1110 valve spring kit. Stick with factory (non magnum) ignition.

Edit....I believe Indy makes a 2x4 Modman intake with carbs and linkage for Magnum.