Jman,
Can't be sure from that photo but it looks like you have a 67 housing and by the look of your spring perches the car originally had mono leaf springs. The mono leafs had a pin that protruded from the bottom and fit into a hole in the shock plate. That's how it looks in that pic anyway, maybe a couple more pics of the springs sitting in the perches?
It looks like multi leaf springs in mono leaf perches, If that is the case you may have to remove the perches and weld on some deeper ones, or modify yours so they are higher and somehow put a hole in the center for the spring center bolt to sit in. I think some of the mono leaf perches sat right against the axle tube, if that is the case and you drill a hole through the center of the perch you would start drilling into the tube. Is the spring center bolt hitting the spring perch? Seems to me the multi leaf perches sit higher off the axle tube to allow room for the center bolt to protrude through.

Maybe if you had a 6 degree wedge, with a hole in it for the spring center bolt, welded to the bottom of the perch? You would also have to check if that would adversely affect your pinion angle.

It also seems to me the multi leaf and mono leaf shock plates have the shock mounting holes at different heights to compensate for the difference in thickness of springs and perches.

I'm just throwing out thoughts i'm definitely not a suspension expert.