Well, that depends. Why are you substituting? Is it a form thing (i.e..dead lifts can be dangerous and possibly harmful until you get your form down pat)?
Or are you just tired of doing the same exercises and want to change it up to have some alternatives? If its the latter, then replacing them gives you another problem. Deads with proper form work legs and back (primarily). So, to replace it you are moving from a compound exercise that involves multiple muscle groups to breaking down to several more isolated movements which focus more strictly on one muscle group each. So, you will have to replace it with several exercises to be consistent and to properly work the muscles.And the disadvantage to doing that....is the compound exercises are natural movements, generate more intensity, involve more muscle groups and use more energy on average.Thus, they work the "body" better than isolating a muscle group. So, they are better for building bigger muscles. You get "all over" strong as opposed to only one working muscle group. So, injury and/or pain aside, I wouldn't recommend getting rid of deads unless you are so well developed that you don't need any more size or muscle mass. Its a great compound exercise for building strength and size. Plus, what is more Grok-ish than heaving a bunch of weight up off the ground with your body??RrrruuuuaaaHH!!!
However, if for some reason I couldn't do deads any more then I would replace them with some of the following exercises:
For Back: Dumbbell Rows (Heavy), Pullovers, Wide Grip Pull Ups, Seated row and Cable (or band) pull downs
For Legs: Squats (Front and/or Back) with a barbell, Dumbbell Lunges,Stiff Legged Dead Lifts (with dumbbells),Calf Raises with weight
If you can just get your....mind together....then come on across to me.....
James Marshall (Jimi)Hendrix