If the heads are cracked are there any alternatives besides the pricey edelbrock aluminums? Can J heads from an LA be reworked to fit, or is that a headache?
i'll echo the others here. it can be done, but not really worth it*.
the magnum head is already a great package on that motor, and performs better than the stock LA head. when you add the complications and the cost into the conversion it's just not worth it.
stock or a little warmed up? keep the stock heads and work 'em just a little.
wanna party? get something aftermarket.
*i can see where there exists a world in which you could score a ridiculous deal on some worked eddie or TF heads and intake that are take offs from somebody's project, and in this world i would maybe, possibly, consider doing the conversion.