When it comes time to align the car it makes it easier.Without the spline the bolt turns when nut is loosened. I believe Gm still sells those bolts. I bought some about year and a half ago from a Chevy dealer. If you do install bolts without the spline the shop might weld them to the frame to keep them from spinning when performing an alignment.
I've replaced them with grade 10.9 metric bolts. I had one break on a brother-in-laws GN as he pulled into his driveway. (That woulda been UGLY had it happend on the freeway)
I've replaced them with grade 10.9 metric bolts. I had one break on a brother-in-laws GN as he pulled into his driveway. (That woulda been UGLY had it happend on the freeway)