My last A4 I use a HL turret ring mounted to the bottom of the turret and epoxy an HL rotation unit on the upper. I don't have the tank anymore but maybe dsgselkirk can post a picture.
I didn't do the elevation on the A4, but what you have here is similar to what I have with the 1/6 Bradley and this is what I did with it. I mount the servo sideways and then strap the servo arm to the post that controls the elevation. The strap has to be loose so it can slide on the pole.
If you are stuck with a HL elevation using you can so the same thing but strap the pole to the wheel.