Will a 96 Chevy rearend fit 2001 1500?

No, a 1996 Chevy rear end will almost certainly not fit a 2001 Chevy Silverado 1500 without significant modifications, if at all. While both are Chevy trucks, the chassis and suspension designs changed considerably between those model years. The bolt patterns, spring perches, axle width, and possibly even the differential itself will be different. You'd be facing a major project involving custom fabrication, and it's unlikely to be cost-effective or even feasible.