That is a correct statement and by using super stock springs, you are increasing the tendancey for this rear steer action. SS springs have more arch than a stock spring, so while you have corrected ride height, you haven't corrected the spring camber and you are introducing roll steer. The more body roll you have, the more exaggerated this will become. This is the reason why stock and handling leaf springs tend to be as flat as possible. The flatter they are, the less the axle moves during cycling.

I might be worth finding an A body main leaf and swapping over 4-5 leafs from the SS pack to see if you can flatten out the pack and get rid of the lowering block and raise you front eye mounting position.

Perhaps before doing that though, you should install the frame connectors and see what impact that has in the condition. A factor that could be contributing to the oversteer condition is chassis flex. Without subframe connectors, the body is moving. This is creating an inconsistancy is suspension reaction. The gians to be had with the connectors overall is why I would tackle their installation first.

There can actually be a few other minor contributors that you may want to keep in mind as you dial this in. I still think body flex is issue #1. Spring camber would be #2, but also factoring in to this could be front shocks that are too soft, too much rear brake bias, a binding in the rear suspension motion, too much rear shackle angle, or too much anti-squat in the spring pack/front hanger relationship.