Hi Veggie i fitted a U anchor which is galvanised and set on a 12" post. It requires drilling/digging a 12" square hole in your concrete garage floor and then filling it again with concrete. I think that it is the best i could have done and here it is. I like it because it is flush with the floor and takes the biggest chain.
Underground Chain anchor,Ground anchor, Galvd.90mm Dia! | eBay