I have exhaust headers, a glass pack, and hollow converters. I figure it would do some good to open up the intake side but I know there is no intake kit for this motor and if I were to fab one would I need bigger injectors?

 

No. The air intake for the 4.9 is the same as the 351- more than enought air for the engine....suggest a wix filter for the oem unit.

 

I agree, it should breathe well enough with a good air filter.