Small animals tend to live shorter lives than larger animals. There are a few theories as to why that is, but the one I believe is most popular is: small animals tend to live shorter lives anyway (because of threats from predators), so there are fewer opportunities to evolve to be long-lived.
The American National Standards Institute (ANSI) Class 150 is a system of dimensional standards for weld neck, threaded, slip-on, lap joint, socket weld and blind flanges. Dimensions for facing, bolts and studs are also included in ANSI Class 150. ANSI Class 150 establishes measures for pipe sizes.
The serial number as well as the model designation may be found on the engine nameplate on the oil sump. For parts information of the 0-360 conventional (or narrow) cylinder flange engines, refer to the Parts Catalog PC-106 to those parts marked STD (meaning standard) for standard or narrow cylinder flange.