[tcabece427]

My guess is the block has been decked. Much of the documentation on the 427 shows a deck height of 10.17". That's not how Ford manufactured many of them. I have a 1972 427 service block and its deck height it 10.19. I had my machinist check this and the piston manufacture. 10.19 is what the piston manufacture (Keith Black) built their compression ratios around. The intake I have Blue Thunder also bolts up fine with no "step" between the head and intake and there is room for the cork gasket at the valley looks like about .125" to .187". The only way to make the intake "fit" properly on a block that's been decked. Is to mill each side and the front and back of the intake. Typically the block at the valley front and back was not milled/decked. Just the top of the cylinder heads.
If you're interested I do have a Ford Police Interceptor intake that has been milled for a 10.17 deck height block.