I don't have a drawing, but I'm pretty sure that the horizontal head bolt spacing is the same as the bore spacing, which is 4.630". Vertical spacing might be the same 4.630" too. You just need a flat plate with the head bolt holes in it to seal, right? I'd check those dimensions on the block with a caliper, and if they're close just lay out the holes on your plate and drill them a little big just in case.