You are correct they should be bolt in not push in. They are out there. I found a NOS set for my 68 L79. They were also used other GM cars my NOS ones referenced corvair rear suspension. I had the GM part number from my originals to search with but can't seem to put my eyes on it for you now. I see restoration shops using them, maybe they will be kind and tell you there source for getting the correct ones for your car. They should look like this.
