My 69 RR, 72 Dart, 72 Satellite, 78 D100, 97 Dakota 2wd amount others all have just a front sway bar from the factory, no rear bar.
Never seen a car with just a factory rear bar.
I HAD a 78 Malibu wagon with just a rear bar....and no sign of ever having a front one. It's not the only one I've ever seen either. Also seen a few trucks with rear bar only.