I have been researching OEM shock inserts and have identified the following part numbers:

56105 E4125 normal resistance shock front

56105 E4185 firm resistance shock front

56205 E4125 normal resistance shock rear

56205 E4185 firm resistance shock rear

Does anyone know what causes the shock to be either "normal" or "firm"? Is it the viscosity of the oil in the shock? Is the the internal valving of the shock?

Also, which shock was installed during original manufacture of the 1970 model year?

Thanks,

Keith

Does anyone know what causes the shock to be either "normal" or "firm"? Is it the viscosity of the oil in the shock? Is the the internal valving of the shock?

Probably the valving. But hard to say for certain at this point.

Also, which shock was installed during original manufacture of the 1970 model year?

Neither. The inserts were for replacement only, not used in original production. The original struts were assembled inside the tube, not self-contained inserts.

I can answer your second question because I have a parts catalog handy, but will leave the first question to someone more knowledgable.

These are the shock absorbers used up to 07/73.

Front

56110-E4125 - US & CAN

56110-E4126 - HS30 2 seater

Rear

56210-E4125 - US & CAN

56210-E4126 - HS30 2 seater

Also, which shock was installed during original manufacture of the 1970 model year?

Thanks,

Keith

US got the soft ones, rest of the world got the firm ones. That would be my guess.