Hello, I have a 1978 ford f250 with a 300 Inline six with a 2barrel on it and I want to do a exhaust on it, but what is the benefit of having the dual efi head versus the single header?

 

They flow better.

 

They flow better that the factory log exhaust manifold but a header would flow better than the EFI exhaust manifolds.
I have found headers leak at the head after some time and you would need to come up with a exhaust system.

I was able to install a complete 94 F150 system in my 81 F100, less cat and added a Thrush welded muffler.
I found the 94 pipes were a little larger that my 81 pipes and why I went with them.
Because I did not run a cat I had to get 2 pipes from cat to muffler to full the gap.

The other reason for running 94 system is I can go to any parts store and get they system.
If I had a muffler shop make up a larger system if I needed a part I would have to go back to them
Just my .02
Dave ----

ps: I am still using the factory log intake and carb trying to get MPG from her