Yeah, the car came with this set up. I know little to nothing about suspension, so, because this set up has worked well so far, I don't see a reason to change, but I am open to suggestions.
I’ll bet you a Gondola from Avanti’s that what you’ve got are Empi shocks with “helper springs”.
I think they were originally designed for Baja Bugs as a quick and easy way to raise the back end of a Beetle being used off road. Plus, they looked kind of cool.
I had a set I used on my pan-based speedsters when I drove them in parades. The homecoming king and queen would sit on the rear lip of the body above the rear bulkhead and use the “back seat” area as a foot rest. It was about 300 extra pounds directly over the back wheels.
I didn’t want to mess with the torsion bars for one day a year, and I didn’t want to drive around for an hour on my bumper stops, so the shocks with helper springs were a nice way to gain some extra spring without really changing anything on the car. After the parade, I would just take them back off and put the regular shocks back on.
I can’t think of a single reason you need them on your car.