None.
Arkansas Code
§27-37-601. Noise or smoke producing devices prohibited.
(a) Every motor vehicle shall, at all times, be equipped with a factory-installed muffler or one duplicating factory specifications, in good working order and in constant operation, to prevent excessive or unusual noise and annoying smoke.
(b) No person shall use on a motor vehicle upon the public roads, highways, streets, or alleys of this state, nor shall any person sell for use on a motor vehicle upon the public roads, highways, streets, or alleys of this state, a muffler, other than as defined in subsection (a) of this section, cutout, bypass, similar device, or any type device which produces excessive or unusual noise or smoke.
§ 27-37-602. Cutouts prohibited.
(a) The sale or use of cutouts on any motor-driven vehicle while on the public roads, highways, streets, and alleys of Arkansas is prohibited.
(b) Any person found guilty in any court of Arkansas of violating this section, in whole or in part, shall be deemed guilty of a misdemeanor and subject to a fine of not less than ten dollars ($10.00) nor more than five hundred dollars ($500).
Antique
Available for historical or special interest vehicles or any vehicle that is forty five (45) years old or older, which is essentially unaltered from the original manufacturers specifications.
Custom Vehicle or Street Rod
Available for Custom Vehicles and Street Rods.
• Custom Vehicle - A motor vehicle that is at least twenty-five (25) years old and of a model year after 1948, or was manufactured to resemble such vehicle; has been altered from the manufacturer's original design, or has a body construction from non-original materials.
• Street Rod - A motor vehicle that is a 1948 or older vehicle or was manufactured to resemble a vehicle manufactured before 1949, and has been altered from the manufacturer's original design, or has a body constructed from non-original materials.
YOM
Vehicles registered as "Antique" may display YOM plates with DMV approval.
SEMA model enacted in 2007. [PDF]