Is there a 2 speed rear end for an 88 Chevy 2500 with 350 and 4 manual trans?
No, a 1988 Chevy 2500 with a 350 engine and a 4-speed manual transmission did not come with a 2-speed rear axle. The rear axles in those trucks were single-speed units. You might find a 2-speed transfer case in a 4x4 version, but the rear axle itself is a single ratio.