1458 ? Did you mean the 1538 ? The 1458 was a tiny movement completely unrelated to that line of watches.
To try to sum things up as this has been rather confusing to everyone here...It seems you want to rebuild a watch using the original case because it has sentimental value, why not, your easiest path will be to have a watchmaker extract the movement of the watch Omega sent you back and fit it in the old case. Yeah Omega told you they couldn't put a new movement in the old case 10 years ago, there might have been a misunderstanding, at any rate it's water under the bridge now.
If not you will have to source a donor movement on eBay/forums as Omega/ETA do not sell movements to individuals and I believe Omega certified watchmaker can only get a new movement if they have an old one to send back. Such movements can be a 1441/1438/1538/ETA 255.461/LONGINES 170.2 and probably others. Then you have the problem of the spacers, hands, joints, etc...It's going to require a lot of patience and dedication !