You could make your own frame extension. Find an industrial shop that sells various metals. You'll need a piece approx. 20" long, 1" x 3"..1/8" thick. It would be cheaper than buying a frame extension already made. However, you'll need access to a drill press and some bolts and lock nuts in order to bolt to the frame and x-member.
I've heard of someone using a dual hump X-member from a Crown Vic or Marquis. It would have to be shortened and have the ends flattened and re-drilled.
If you choose to make your own extension, I can get you the dimensions for the holes.
I also have the MOOG #5606 springs up front. I did sit high when I first installed them years ago. It had settled over time, but it seems to be sitting high again. I've have the complete front end off the car for for almost a year. I guess it would have to resettle.