If you want to work lower back, GENERALLY Stiff legged deadlifts are the best. good mornings are ok, but you have to be careful. Weighted hyperextensions are the most direct exercise fo this region. I do regular deads, but since I do them so heavy , and along with very heavy squatting I get enough lower back stimualtion, but that's me.
If its hamstrings you wnt to work, try a superset of some type of leg curl movment and stiff legged deadlifts-the first movement will prexhaust the hamstrigns and remove the weak link- the lower back thus putting more stimulation on the hamstrings. Good luck