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15426378: like 2+2 said 7 and 8 wires seperated as far as possible. they fire after each other and the cylinders are next door neighbours
13726548: 5 and 6 wires seperate for the same reason
18436572 in a GM is the same as 15426378 in a Ford, if you number the cylinders the same way. I've had 18436572 in my head since my teens (a long time ago) and still use it to wire a Ford. At least this holds true for 289/302, I know some engines have different firing orders, just too lazy to look it up.