Guys I took my LT1 to a shop to get installed the felpro header gasket because of a leak, but now the car has the abs inop light on , does the LT1 has some sensor on the back wheels that are related to that light?

 

There are multiple reasons for the ABS light to come on. I would suggest looking at the front ABS harnesses for possible burns as you just had the header gaskets changed (the harnesses run down close to the headers). Yes there is a sensor in the rear (mounts at the top of the diff.); 2 sensors, one at each wheel, if you have traction control.