If you can get single leaf springs for a similar price to multis I would say go for them. They became the standard fit on later capris and are fully compatible, just better. Changing to single leaf springs seems to be popular everywhere except in the US -there were no standard spec Capris sold there with single leaf springs so it just doesnt occur to them as the way to go.
This is the information I was given by other forum members when I fitted new springs.
Tools: 7/8 ths or 22mm offset ring spanner. 19mm ring spanner. 13mm Spanner. 19mm, 17mm, 5/8ths or 16mm & 13mm sockets.
(actually imperial but these are nearest metric sizes)
Replacement rear shackles - the originals have a tendency to shear if they are being at all awkward
Replacement U-bolts - standard Ford items - do not be tempted by the likes of Grayston or rubbish ones
Front bolt - if it will not rotate - jammed into the bush (likey)
WD40 or Plus Gas.
Copper grease for reassembly
When you change the springs, it could be an idea to adjust the anti-roll bar .. it does help.
jack up the car body as high as it goes and support the body allowing the suspension to drop free. but be prepared to support the axle in place when the springs are removed !
Spray every fixing in WD40 (or suitable alternative)
1/ loosen the 4x 1/2" nuts securing the rear shackles, but leave them in place loose.
2/ loosen the 4x3/4" nuts securing the axle U-bolts ... but leave them in place loose
3/ loosen the 2 front spring bolts - note that the nuts are inside the sills, you have to use a swan neck ring spanner but may be able to use a 1/2"drive socket and T-bar with removable head ..
loosen the nut a wee bit first, then unwind the bolt using a ratchet, holding the nut with the socket... if the bolt refuses to spin out, leaving the spring bush, and the nut in place - problem ..
Instructions in case front bolt is jammed
1/ cut the spring thru about 6 inches from the retainer
2/ rotate the dod of spring as far down as it will go to expose the section around the bush - cut thru that - grinder or welding torch, remove the bits of spring, cut into the springbush shell, burn off the rubber, split the inner steel tube - and then remove the bolt !! THAT is usually the worst case scenario problem when replacing the rear springs - it can be a total BITCH but it can be done
Clean up the nuts and bolts and apply copper grease to the length of the bolt. This will prevent seizing problems in the future.
The new spring should be attached front and rear first. At the moment, don't bother tightening up the bolts fully.
Re-attach the centre of the spring to the axle. Put the trolley jack under the front part of the spring and slowly raise the spring upwards. Make sure that you have fitted the metal and rubber parts from the old spring.
To help with the fitting, cover the topmost rubber pad with some copper grease. You may have to tug on the axle a bit to get it aligned, but eventually you should be able to jack the spring into place ready for clamping. Attach the new U-bolts (copper grease on the threads) through the lower clamp plate and fix the 4 nuts on. Tighten them up slowly in sequence making sure that the same amount of thread is visible on each. Eventually you can torque them to 20 pounds foot (repeat several times until all 4 are properly torqued). This is not the final torque setting that should be done at the end with the car on the ground
Once the other side is finished you can attach the road wheels and lower the car down. All the bolts should now be tightened and torqued to the correct level with the car resting on the ground (Rear = 9 pounds foot, front = 28 pounds foot & spring U-bolts = 25 pounds foot)