Let's see...$2K...Well, if the Magnum runs well now... I'd pull the heads, have them set up for performance, maybe a little bowl cleanup, good springs, retainers, etc. I'd mill them about .020, and have them drilled for the LA intake pattern (easy deal for a shop) and gasket matched for the LA port. Run a hydraulic roller cam, reusing the lifters and spider setup. Get a Performer 340/360, and drop it in. No rebuilding of the lower end, I'd leave it totally alone. If you take it apart, you "might as well" rebuild it, better pistons, etc. But if you dont have to, dont bother.