Any firearm involved in any violation of the provisions of 26 U.S.C. Chapter 53, shall be subject to seizure, and forfeiture under the internal revenue laws: Provided, however, That the disposition of forfeited firearms shall be in conformance with the requirements of 26 U.S.C. 5872. In addition, any vessel, vehicle or aircraft used to transport, carry, convey or conceal or possess any firearm with respect to which there has been committed any violation of any provision of 26 U.S.C. Chapter 53, or the regulations in this part issued pursuant thereto, shall be subject to seizure and forfeiture under the Customs laws, as provided by the act of August 9, 1939 (49 U.S.C. App., Chapter 11).