What is the clue that convinces you that the Abner Smith of the 8th Arkansas is your man. Does the information provided in the documents of the 8th agree with your families records?

The A. Smith of the 10th Arkansas was raised with men from Van Buren and he has an approved Confederate pension issued while he was living in Van Buren.
Obtaining his pension file, procured through the service noted in the Red enclosed box above, may provide additional clues for you.

Here is a listing of all men I've found with the name A. Smith from Arkansas units.

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I do not find an A. Smith in the 7th Arkansas Infantry

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A. H. Smith, Private, Company E, 16th Arkansas Infantry, enlisted February 15, 1862 at Carrolton, Arkansas, by N/E. A. Evans for one year, furloughed from hospital June 18, 1862, recorded on the July & August, 1862 as absent, sick at regimental hospital, no further records

[The Sixteenth Arkansas regiment was organized in November, 1861, near the present town of Rogers, Benton county]

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A. H. Smith, age 23, Private, Capt. Evans' Company, 1st Regiment, McBride's Brigade, Arkansas Infantry,* enlisted February 15, 1862 at Carrollton, by Capt. N. A. Evans for one year, deserted April 25, 1862, no further records

* This company subsequently became (Old) Company B, Shaler's Regiment Arkansas Infantry. The regiment was also known as the 27th Regiment Arkansas Infantry

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Arkansas Confederate Pensions

Surname: Smith
Given Name: William Abner
Application Number: 27849
Widow Surname: Smith
Widow Given Name: Martha Jane
Company: A
Regiment: 10
State Served From: Arkansas
Division: Cavalry
Pension County: Conway
Death Date: 3/3/1925
Application Year:
Widow Death Date: 8/8/1932
Comments: widow applied 1927 / questionnaire

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Arkansas Confederate Pensions

Surname: Smith
Given Name: A. H.
Application Number: 13058
Widow Surname:
Widow Given Name:
Company: K
Regiment: 10
State Served From: Arkansas
Division: Infantry
Pension County: Van Buren
Death Date:
Application Year: 1907
Widow Death Date:
Comments: approved

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A. H. Smith, Private, Company K, 10th Arkansas Infantry, captured at Port Hudson, La., July 9, 1863, released on parole July 12/13, no other records

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10th Regiment, Arkansas Infantry

10th Infantry Regiment was organized in July, 1861, at Springfield, Arkansas. Its members were drawn from the counties of Cleburne, Van Buren, Conway, and Perry. The regiment moved to Union City, Tennessee, where 150 men died from the effects of measles. Later it was involved in the conflicts at Shiloh and Baton Rouge, and in October, 1862, contained 249 effectives. Attached to Buford's and Beall's Brigade, Department of Mississippi and East Louisiana, the 10th was part of the garrison that surrendered at Port Hudson on July 9, 1863. After being exchanged, the men returned to Arkansas and were reorganized as the 10th or Witt's Cavalry** Regiment. The unit skirmished in Arkansas and on May 28, 1865, requested from the Federals terms under which it could surrender. Its commanders were Colonels T. D. Merrick and A. R. Witt, Lieutenant Colonels S. S. Ford and Luther R. Venable, and Majors C. M. Cargile and Obed. Patty.
http://www.civilwar.nps.gov/cwss/regiments.cfm

** There is no A. Smith in the rosters of this regiment in any of the on-line lists