Broke both lower shock mount studs on a 58 impala but we found a solution. 1958 impala is a one year only shock stud according to all catalogs and internet’s sources. Retailed at $250 for a pair!. We discovered that using two passenger side 59-64 impala shock studs give the same results. Free if you have em laying around like we did or can be bought for under $100 used.