The split is due to the cold intake ports and hot crossover, most likely would warp more without them. You can have it machined and if the heads have been milled that's OK. When the heads and/or deck are milled the heads sit lower and closer than if they were not milled and the intake manifold ports sit up slightly higher than normal, when a lot is taken off the deck- head mating surfaces the manifold is machined to correct the alignment. You could gasket match after it's machined. If the intake sits too far down us a thick intake gasket.