My response of "Cavalry" was to offer a correction of the word "Calvary"; an oft used and incorrect word for mounted troops.

As to the 40 series regiments, our friend Bryan Howerton had this to say on this board some time ago:

Posted By: Bryan Howerton
Date: Saturday, 9 November 2002, at 6:51 p.m.
In Response To: 46th Ark. Cav = 46th Ark. Mtd Infy? (Hayes Lowe)
They are one & the same. The 40-series Regts were initially authorized by the State Military Board as Infy Regts. The decreasing availability of fodder for horses in 1864 led the Trans-Ms Department to issue an order proscribing the raising of any additional Mtd Regts in Ark. However, when Sterling Price received authorization to campaign in Missouri that Fall, several of the new Regts were Mtd in order to accompany him. As a result, the 44th, 45th, 46th, 47th, & 48th Ark Regts became Mtd Infy Regts. They were rarely referred to in contemporary reports & orders by numerical designation. Price referred to them as McGehee's Cav, Crabtree's Cav, etc., which eventually resulted in their later being referred to as 44th Cav, 46th Cav, etc.

Posted By: Bryan Howerton
Date: Monday, 17 November 2003, at 9:35 p.m.
In Response To: 45th Cav (Randell Woodam)
Randell -- There's not much information available on any of the 40-series Ark Regts. They were organized in the late spring of 1864, mostly in northeast Ark, to beef up Sterling Price's force in preparation for the Missouri Campaign.

The Regt was technically designated as the 45th Ark Mtd Infy, but was commonly referred to as Baber's 45th Ark Cav. Col Milton Dyer Baber was captured during the Missouri Campaign, so after Oct 1864 it was referred to as Clark's Ark Cav (Lt-Col James W. Clark succeeded Baber as Regimental Cdr). Many of the men in the Regt had served in the 38th Ark Infy.
You'll probably have more luck searching for references to Baber's Ark Cav, rather than the 45th Ark Regt.

The 47th Ark Regt -- officially the 47th Ark Infy (Mtd) -- usually called Crandall's Ark Cav -- was one of a half-dozen or so Regts organized in the spring & early summer of 1864 to accompany Price in his Missouri Campaign that Fall. The 44th, 45th, 46th, 47th & 48th Ark Regts were organized in central & northeast Ark, & consisted of conscripts & men absent from other Regts for various reasons (on leave, on detached service, absent without leave, etc.) These Regts were decimated in the Missouri Campaign, but most retained their organization & surrendered at Jacksonport in June 1865.

Other Regts were dismtd in Aug, & very few other Mtd Regts were authorized until preparations began for Price's Missouri Campaign of 1864, when the 40-series Mtd Infy Regts were organized (44th through 48th Ark Regts).