Rear enders in pre72 bugs can rip the seat off the rails and send you head first into the rear window as the car gets shot forward. Procar seat rails bolt to the original pan rails and are way more robust than the original. The tilt mechanism is also beefier. Reinforcing the rails-to-pan welds is also a good idea.
Another rear end safety mod is a
third tail light and
rapid flashing brake light module. The blink really caught my attention on a New Beetle I saw with this flasher module.
Nothing beats luck with good defensive driving.