What you're seeing when you're looking at the hood is called "Crab walking". Basically it means the rear axle is not square with the body, causing the thrust angle to be off (basically the rear axle is driving straight down the road, but the body isn't).. when you're in the driver's seat, you turn the front wheels slightly to compensate for the angle being off, and there you have it... crab walk.
You need to go back and re-check everything in the rear spring mounts, axle perches, etc. Something is not right. Take it all apart and re-check the lengths of the front and rear portions of each spring, double check your perches and note any extra openings in them and make sure that you get the center pin right in the center hole on the perch when you put it back together. Once it's back together, double and triple check the u-bolts for tightness, and break out the tape measure and take some measurements to see if it's square now. With the front wheels straight, the measurement from front passenger to rear driver tire should be the same as front driver to rear passenger. Distance from passenger front to passenger rear should also be the same, and driver's front to driver's rear.
