We recommend that the rear telescopic shock absorber kit is used with softer rear springs than the standard 7-leaf springs which we feel are stronger than necessary even for those that have passengers in the rear. When we fit a 4-seater rear telescopic kit we usually remove the rear springs and convert them to 6-leaf springs. See Converting from 7 to 6. 

For those who require maximum ride comfort and never expect to drive their 4-seater fully laden with four adults and a full luggage rack, it is possible to change the rear springs for 5-leaf springs. These combined with the quality telescopic shock absorbers provide the best control for the 4-seater rear suspension.

FITTING INSTRUCTIONS

1. Remove the rear seats, seat floor pan and shock absorber covers. Mark the position of the vertical edge of the shock absorber covers on the plywood heelboard. It is better to remove the front seats for access, and essential if the springs are to be removed as well.

2. Wedge blocks between the bottom of the rear springs and lower chassis flanges to give access to the U-bolt nuts.

3. Raise the car and support securely.

4. Disconnect the Armstrongs lever arms and remove. Remove the u-bolt nuts, u-bolts and original spring clamp plates. (If the rear springs are to be removed for modification or replacement now is the time to undertake the change.)

5. Remove four 1/4 nuts and bolts on each side and remove the lever arm shock absorbers complete with mounting plates.

6. Fit the u-bolts and new spring clamp plates with the shock absorber pins at the front. Tighten  u-bolt nuts evenly.

7. Remove the packing blocks and let the axle sit on the rebound rubbers.

8. Hold out of the way the rubber matting on the heelboard and cut the plywood panel to make clearance for the top of the shock absorber. See sketch adjacent.   
 

9. Position the new shock absorber mounting plates with the top brackets pointing backwards and located under the seat angle iron frame. The position of the side brackets is usually close to the position of the original lever arm side plates. The aim is to position the side brackets so that an almost fully extended shock absorber fits on both mounting pins as upright as possible. Bend the top mounting if necessary so that it is flush under the seat frame.

The top bracket fits under the seat crossmember close to the weld where the crossmember is attached to the seat frame sides. Later cars with integral seat belt mountings have seat frame sides of 1 5/8" width, early cars have seat frame sides of 1 1/4 width. On the later cars the top bracket of the shock absorber mountings must be fitted right up to the weld of the seat frame. On earlier cars there should be 1/4" to 3/8" between the top bracket and the seat frame side. See sketch below.

10. When the best position has been ascertained, clamp the side plates in position on each side, mark and drill four 1/4 holes through the chassis holes and drill 1/4 holes through the angle iron seat frame and the top of the shock absorber mounting bracket.

11. Bolt the mounting plates in position with the 1/4" nuts and bolts supplied. The 3/4 long bolts face outwards through the chassis and the washers are used under the nuts on the outside of the chassis. The 1" long bolts go down through the seat frame and the top of the shock absorber plates. (The car may need supporting under the axle to move the springs in order to give access to fit the lower of the four side mounting bolts.)

12. Fit the shock absorbers but do not tighten the nuts. Adjust the brake hose if necessary for clearance.

13. Lower the car to the ground and settle by bouncing once or twice. Tighten the shock absorber nuts ensuring that there is clearance between the lower end of the shock absorber body and the u-bolt mounting plate. Also at this stage, tighten the spring mounting bolts and nuts if the springs have been removed and refitted or replaced.

14. Refit the shock absorber covers (which may need slight bending to clear the top of the shock absorber brackets), the seat pan, seats, etc.

15. Road test. If using Spax, or Konis adjust to the required setting which for road use is usually the softest setting.

I rebuilt my 66+4 rear suspension about 5 years ago.  Used the Rutherford engineering individual towers "bolt on kit" made for the 4 seater (these fit in the original "shock boxes" in the rear footwells and are tied together using the "bar" that forms the front of the rear seat bottom cushion).  I highly recommend the setup as it uses the "long" Koni's or Spax shocks (as Lorne notes this gives maximum travel).

For the springs, when I rebuilt in early 90's I put in new 7 leaf springs then, when converting to the Rutherford system Dave Rutherford was kind enough to give directions on how to cut a 7 leaf system to replicate a 6. See below.

go from 7 leaf to 6 leaf by

remove leave 5 (3rd from the axle)
leaf one stays the same (duh! it has the shackles)
leaf 2 stays the same (tied to leaf 1)
leaf 3 cut the front portion to 15.5 inches from 18.25 inches
leaf 4 cut the front portion to 12.5 inches from 15.75 inches
new leaf 5 (old leaf 6) unchanged
new leaf 6 (old leaf 7) unchanged

You'll need to shorten the shackle bolts or have new ones made.  Don't forget to grind the new cut edges and oil between the leaves.