Hi John.
The front springs on the heavy haulage S26 vehicles should have the same springs as the Scammell S24 Part number HDK1541 made by Jonas Woodhead RSR ltd, the front spring Ubolts were made by Skidmore & sons in Walsal Part number NDK3487. The best vehicle to have a look at would be your friend Dave Crouch's S24 4x2 recovery.
I maybe able to get a drawing of the springs if that is any help.
you can give me a call via the number on my website if you need more info.
regards
Clive