Coil over shocks should do nicely for both the front and rear. You could move the rear torsions up to raise the rear making the rear torsion bars hold more. Coil over shocks are still a good addition. How are you having a hard time finding parts for the VW. The world is full of parts and parts houses and a gamut of after market parts abound world wide.
What were you or are you thinking of for fixing your issue? You could also ditch the lead and get lithiums
Do you have disc brakes both front and rear in your heavy lead sled? You need at least disc brakes up front to handle the extra load.
You could also just accept the new height of the vehicle and put on Coil-Over shocks. How much extra weight are hefting around?
My 64 Ghia had 1020 lbs of lead. Ouch.