If its cracked ,it going to get worse and go further, especially if its at a susp. mount point..You should have it sleeved and rewelded befor driving it anymore!!!! even puttin the car around its gonna flex
Always check the dates on them before buying (hard to though if you mail order) but i needed a set for my race truck went to a local race shop here in town bought them got them home went to put in and noticed they were dated 2years old already!! so had to take them back..