Jesus, if that hack job of an exhaust system is any indication of the way that motor was put together, I'd be yanking it and starting over from scratch
Yeah why do stuff 2 or three times. Also you had better get a service manual for your car or at least a small block book. It has the firing order in it. I always pull the block drain plugs out when I pull a set of heads off
just so I don't fill the cylinders with coolant and make a big mess on the floor.