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.

 

ah crap, I had my head up my rear. I thought that firing order looked a little off but was too lazy to look it up.