When you remove the original front springs check if the A upper diameter (picture 1) is the same as the ULTIMATE spring upper diameter: If it's the same diameter wind up as the original fitting (picture 2). Otherwise you have to fit the dishes included in the complete kit or the set of springs (picture 3).

2 / What is the right complete kit or set of springs for a PEUGEOT 405 TD?

On this vehicle there is two original different fittings for front springs. In order to choose the right one you have to measure the length of the original springs when the car have the wheels putted down on the floor . .

3 / I have a 306 turbo diesel what is the right complete kit or set of springs for my car ?

The ULPEUG32 kit or the AE265160 set are available for the 306 D Turbo ( 3 Doors car with sport chassis).
The ULPEUG31 kit or the AE265152 set are available for the others version of turbo diesel 306 ( like 306 XRDT, SRDT, Etcƒ)

4 / Original parts must be adapted ?

Yes , particularly the bump stop ; you have to divided them by two in order to avoid the bumping effect.

5 / Can I fit lowering springs with original shock absorbers ?

With a small lowering you can fit the springs with original shock absorber . But, be careful the shock absorber have to be in good condition moreover the high pressure gas shock absorbers can not be fitted with lowering springs.