1. Mesure the length of the shock absorber at rest.
2. Jack the car up by the chassis, and secure with the axle hanging just off the ground.
3. Unbolt the springs from the chassis.
4. Unbolt axle from Springs.
5. Cut 'chocks' (that were sandwiched between axle and spring) off of axle.
6. Weld the chocks back on (or make new ones) 180 degrees around the axle from where they started.
7. Bolt the springs back onto the chassis.
8. Bolt the axle back to the springs with the original u-bolts and backing plates.
9. Use the mesurment from step 1. to work out where the top of the shock absorber needs to be, as the bottom mount will now be higher than it was originally.
10. Make new top shock absorber, and atatch to the chassis.
That's about it. You need to check the u-bolts are tight every few weeks for a while after the conversion. The pick up version of the 4trak has a spring over axle as standard on the rear. Though I don't know if the 'chocks' are the same distance apart.
Personally I wouls scrap that idea, and go for a body lift. Basicle stand the body on legs (where the body mounts are) over the chassis. This will give you the same hight (or more), alow you to fit bigger tyres, and not lift the centre of gravity as much as a suspension lift/spring over conversion.