Damon,
I have previously posted just about all that I have on this regiment.
As far as I'm concerned, Bryan is the expert on the Arkansas State Military Board's process for naming/numbering Arkansas regiments.
As an example, long ago he posted this:
In the State Military Board’s straightforward view of the world, Cocke’s Regiment (shorthand, remember) was simply the 39th regiment of infantry listed on its Wal-Mart notepad. The outside world said, Fine and dandy, and then proceeded to ignore the Board’s careful numbering scheme. For a short period of time, some authorities were referring to Hart’s 30th Arkansas Regiment as the 39th Regiment, adding to an already confused situation. Then there was the anonymous military genius on General Sterling Price’s staff who decided to designate all the Arkansas infantry regiments in the District of Arkansas as Trans-Mississippi Rifle Regiments. Cocke’s Regiment was designated as the 6th Trans-Mississippi; and, just as surely as day follows night, the officers and men began referring to the regiment as the 6th Arkansas.
Thus, it appears that the rifle regiment designations were not employed until Price returned to the Trans Miss Department in the spring of 1863.
Coincidentally, Price initiated a renumbering of the Missouri regiments as well:
8/17/63 HEADQUARTERS DISTRICT OF ARKANSAS, Little Rock
General S. COOPER, from Price
......................................................................................................................................................................................................
It seems that the officer who bore the April muster-rolls of Frost's brigade to Richmond reached there in advance of the bearer of the other muster-rolls, and that the regiments of that brigade (Clark's and Mitchell's regiment and Musser's battalion) have received the numbers which had been given to the regiments in Parsons' brigade. I beg leave to submit the matter to your attention, and to beg that you will designate officially the numbers which these regiments shall respectively bear. Until then I shall not give any further orders on the subject.
I will defer to Bryan on the chronology of the various designators for Trans Mississippi Arkansas regiments.