Enhance the performance of your 1970-1976 GM 250 4.1L engine with this set of 6 Autolite 147 spark plugs. Made of high-quality copper material, these spark plugs have a thread diameter of 14mm and operate at a voltage of 12V. They are compatible with R46T and ARF8 interchange part numbers and OEM part number 5613357. These spark plugs are suitable for gasoline fuel type and have a standard configuration. They are not vintage parts and do not come under the category of performance parts. Buy these reliable spark plugs from Autolite, a trusted brand in the automotive industry, and enjoy a smooth driving experience. Exact item lot is shown. New old stock spark plug set with original packaging. Items have very light surface rust, which will not affect performance. Made in USA. No returns on installed items or partial lots. Please review our business policies in our store for information regarding returns, shipping and warranties.