I have just puchased myself a 69 Beetle as a basis for a beach buggy project and I have noticed that the equaliser spring assembly has been removed by one the previous owners. My understanding is that VW only installed it on a few type one models. My question is what exactly does the equaliser spring do and is it an essential peice of equipment that I need to think about reinstalling?

When the beetle is carrying extra load (passengers in the rear) the "equaliser spring" then helps to increase the spring rating by sharing the load.

Thanks Craig, can I get awat with out having one if I install heavy duty rear shocks?

yep