Ok This is how you do it on a Fourtrak.

1. The bottom plates that the springs sit on (the flat plate that the U bolts go through)also have a pin attached that acts as the lower shock mounting.Undo this nut.Undo the nut holding the top of the shock to the frame. Remove the shock (keep all nuts ect in a tray so you can find them when you refit the shocks.

2. On a Fourtrack the handbrake cable is mounted at one point on the rear spring..this has to be undone. (not sure if Sporty has this arrangement)

3.Before jacking up the vehicle loosen (dont undo all the way)the leaf spring attaching nuts (the large nuts that go the through the bushes at the ends of the springs.

4.Again without jacking up the vehicle loosen the U bolt nuts (dont loosen all the way)You may need to get some heat on the bolts to free them off..they will be very tight and probably rusty. Make sure your spanner or socket has a really tight fit and tap hard with a hammer to free them..I could not have freed mine off without heating them first.

5.Using the chassis frame jack the vehicle up...now remove the U Bolts (put an axle stand under the axle when carrying out this bit)

6.Once the U bolts are off,take the axle stand out and slowly jack down the vehicle. The axle housing should clear the leaf spring.

7. Now you need to undo the shackle bolts (the short flat metal strips that hold the springs to the chasiss frame at the rear end of the front springs spring .The rear springs have shackles at each end of the spring .Two bolts on each shackle to undo.Again heat may be required to free them off.If your doing the front springs the other end of the spring is attached to a bracket...loosen this bolt.

8.Tap the shackle pins halfway out (the pins that go through the ends of the springs)Remove the spring off the pins (rear spring has two).You should now be able to remove the springs.
Tap the shackle pins all the way out of the frame.
If you were provided with new shackle pin bushes that fit into the frame (chassis)you will have to remove the old ones in order to fit new ones...knock em out.And fit new ones if you have them.

9.I dont know if your new springs come with the spring bushes already fitted..but if not you need to fit spring bushes to your new springs. They will be a very tight fit ( a tip is too heat the rounded end of the spring till its very very hot and then hammer in the bush.Make sure you keep it straight as you hammer it home and dont burn yer fingers.( I used a large vice to hold the spring steady)

10.Once the spring bushes are fitted you are ready to fit your new springs to the car.Insert the new shackle pins half way..connect the spring to the bottom shackle pin..then tap the shackle all the way through the frame and spring.Do this for both ends for rear springs...after fitting the plate to the other side of the shackle get yer nuts on (oooer missus)and tighten them temporarily.

11. Once the springs are in place you need to jack the vehicle up so that the springs meet the spring 'plates' welded to the axle.
Get your U bolts and position them over the axle each side of the spring.Offer up the lower plate (spring seat) and guide the Ubolts through the holes. Get yer nuts on and tighten them up evenly.They should be torqued to the specified value found in the manual.
The nuts should be tightend in such a way that the protruding ends of the bolts are of equal lenghth.

12 Re-attach handbrake clamp (if fitted to the Sporty).

13 Slowly jack down the vehicle...gently rock it from side to side so the springs settle.

14. Re-attach the shocks

15 Finally ensure that all bolts and nuts are tightend to the specified torques found in the manual.

Ron... if you dont have a manual may I strongly suggest you buy one of Lurch..its only £15..there are really clear illustrations to take you through this job step by step.
There will be differences between the Sportrak and the Fourtrack..I have only done springs on the Fourtrack (rear ones.

I have tried to give clear instructions on how to tackle this job but I take no responsibility whatsoever for anyone else carrying out the job.

Hope I have been of help.