Bore spacings are alike.....valve sizes.....port volumes.....intake to exhaust flow rates (exhaust ports do NOT work, most LS7 camshafts have 20-30 extra degrees of duration built into the exhaust side, which is similar to a Cleveland, where it's not uncommon to add another 8-12 degrees of exhaust duration), exhaust port spacing, etc, etc. Now obviously it's not a direct copy, because technology has advanced in the last 40 years, but the LS design is 180° out from the traditional SBC and is much closer to a Ford. Compare an LS7 head to a 4V Cleveland head some time.
Another added bonus, when you convert an LS engine to a carb/distributor setup, you use an MSD Ford 302 distributor.
I have no clue why people are putting LS heads on Fords. Probably because LS engines can be bought for pennies on the dollar and since the heads do so well, it's a potential for an easy power adder. Plus, it's just hot rodding nature I suppose. When you have a Ford 302 that has 160 cfm intake ports on factory heads and you can bolt on something that approaches 300 cfm, I could see the attraction....