Pullovers should be part of any chest routine. Use them as one of the last exercises of the workout after other muscles are already fatigued.
Finish your next chest workout with dumbbell pullovers: 3-4 sets of 12-15 reps. Focus on squeezing the pecs to initiate the movement up from the bottom position and work on holding the squeeze throughout the rep.
A bar takes the ab rollout to the next level. Try a wide grip to hit the chest and shoulders as well as the abs. Have a super strong core? Narrow the grip.
Anytime you plateau in training, it's rarely because your program isn't complex enough. Usually it's because you've strayed from the basics. Here's an overview of the basics of training.