header install questions

I am building a 408, and will be in,stalling hooker 5116 headers. My question is how is the best way to install them? The car was converted to manual steering for clearance. Do I place them in the bay them installing the complete motor around that? Or install the long block, then the headers then the heads? Or install the complete motor and then the headers? Or any other methods would be greatly appreciated. I want to make this as easy as possible