Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 321574R91 found under Cap Assembly Protective Muffler by Navistar Intl Corp. The National Stock Number assigned to this part is 2990001220658, and the Federal Supply Class is 2990 Miscellaneous Engine Accessories Nonaircraft. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 321574R91.