The axle is kept straight by adjustable trailing arms made from 2" box with rubber bushes one end (which fit in the original spring yolks) and 20mm rose joints on the other.
The top arm is made in the same way but had to bend in 2 places to avoid the underside of the car
The two highest points of the chassis kick-ups are bridged with a piece of 10"x4" channel. The rams are mounted through this so all the load is on the chassis and not the body. They have a screw-on ball end which sits in a cup (known as a power ball) that is welded to the flat surface on top of the axle.
On the bridge I've used pipe flanges to make carriers that let the rams swing forward and back while keeping them straight.