Randy,

You may want to try and get info on some of the few surviving articles of C.S. enlisted clothing that have a Shiloh provenance. At that early stage of the war the uniform situation seems to have been like it was at 1st Bull Run. The regiments were getting whatever they could from their respective states and local communities. Often you could have different companies within the same regiment uniformed differently. The Crescent regiment from Louisiana has 2 surviving uniform items attributed to being worn at Shiloh. One was a shell jacket worn by a soldier in Company C and the other a frock coat worn by a soldier in another company.
Tennessee and Arkansas both seem to have been producing
frock coats for issue to their regiments at this time.
There basically seems to have been a wide variety, every thing from undyed white jackets and trousers of the 2nd Texas, blue uniforms of some Louisianans, to the familiar gray and butternut. From my observations of photos of C.S. troops from that stage of the war it seems to me that the most common garment for an infantryman was a frock coat.
Basically though A.S. Johnston's boys seem to have worn a bewildering variety.