Help with flexplate

Does anyone know where to get a flexplate for a 340/727 transmission with a symmetrical bolt pattern for the converter. I'm getting 3 bolts in and the last hole doesn't match up it's about a half a hole off. I'm sure it's a newer converter which is causing the problem here just dunno if I can use a flexplate for a newer vehicle and have everything still match up. All advice is appreciated

Usually it's a lot simpler to egg the hole enough to get the bolt in.