Crabbing

Today was the first day that I drove behind someone else driving my 73 scamp. On the freeway there is a small but noticeable crabbing going on. The front is stock. The rear end was narrowed (so perches moved). 8-3/4. New ss springs. The shock plates needed a sleeve to match the hole size and pin on the leaf spring. It is not snug, maybe 1/16 inch slop. I also needed to place 4 degrees shims to correct the pinion angle. Where do I look to make changes to the alignment of the rear? When going down the road the front left is more left than it should be