I see a lot of Camaro and Mustangs using a crossbar between the down bars on aftermarket suspensions but I don't think I have ever seen one on a Nova. So, is the crossbar needed on street-only cars? Here's a pic of one on a Camaro:
It's just like a strut brace on other cars...it stiffens the front suspension/body and helps minimize body flex during hard cornering. I don't think there are many Novas being used for road racing or auto-cross, hence the reason we don't see braces on Novas.