Leaf Spring/Ride Height

Trying to get the rear ride height up on my 70 Dart/440. I just changed from the 5 leaf springs it came with, to some 6 leaf springs, off a 340 car. That got me 3/8 " NOT ENOUGH. Looking for about 3" of rise from where it is at. It has sagged about an inch below stock, I think. If I add another leaf to the 6 leaf spring pack, would that help? Thinking about adding the 2nd leaf down from the old 5 leaf pack, onto the 6 leaf set up. So I'll have a 7 leaf spring. Has anyone done this? Shouldn't this help the ride height?