The Aussie Crosss-flow head to American block mating trick doesn't need a sleave job if you have the right pistons. Australians used to perform this sort of trick on there ancient 138 cube Holden Sixes. A dude called Merve Waggot used to add a 500 thou steel plate doweled on the block, throw in a custom crank, and end up with 180 cubes. Another Australian guy had a jet boat 350 Chev bowtie block (in his Capri!) which had been decked 125 thou because the class wouldn't allow hi-compression pistons. He just added a 1/8 inch copper gasket and made sure his pistons were the right type so the upper rings didn't do the mambo with the ridge formed. Turbo installations on the Oz 250 Cross-flow had two gaskets and a 62.5 thou spacer plate to lower the compression. So this idea isn't new, and if done by someone with good machining practice, then it works.
Without the pain of doing a foreign exchange, the best option is to use the standard US head and grind the intake off, and add a mild steel or ductile iron adaptor plate. This used to be done in Australia too, but they used a special alloy manifold which took some odd -ball contant depression carbs like Jag style SU and Stromberg CD 150/175. The speedway guys used to consume a large amount of these. Argentina has a special detactable manifold version which is better, but useless if it you don't have one in your posession. The latest Chev 4200 OHC motor has the same bore centres as the Ford (and Holden sixes..looks like the engineers must have copied each other), so the intake mainfold could be made to fit if you can track one down at a parts yard...and make allowance for the fact that it is a cross-flow engine too. The Australian Cross-flow carb manifold has a 3 degree tilt in the wrong direction because its got the carb on the left, and won't suit the right hand side of the US 200/250 without modification.