Chevrolet Silverado

I am in the final phase of rebuilding a 2002 Chevrolet Silverado 1500HD 4WD 4dr CrewCab P/U and need some advice. I replaced the engine and transmission (new from GM) and the transfer case (used from recycler), I purchased a dash cluster from a recyler and had it checked and serviced. The truck runs fine but my speedometer (mph) needle does not register my speed. I replaced the spped sensors (2) in the transfer case, but the needle still justs lies there dead, incidentally, all other gauges on the dash cluster work fine. Is there something i am missing, where do I look next to solve this problem. My check engine light is on. Also, I need help in evaluating why my ABS light is on. Any suggestions what to do? Thanks for the help. Once I solve this, I do have a few other questions but they can wait.