Assuming a 5 gallon batch.
1.5 Oz. Magnum at 60 minutes.
.5 Oz. Centennial 30 minutes.
.5 Oz. Centennial 10 minutes.
1 Oz. Citra flameout, 20 minute steep.
That should give you about 80 IBU's
Keep your dry hops the same.
I think you would be very happy with that. I've done Citra with...