@kazd You just need to be mindful about wording used to inquire for help looking for parts as there are rules about WTB (Want To Buy) posts. In your case, I took it as trying to get some advice on how to find movements, but it can be interpreted as a WTB.
To answer your question:
Use this resource to find the PDF data sheets on the calibers and find out which parts overlap from different version of the base movements. Search Omega 684, 683, 680, 685.
https://www.cousinsuk.com/document
Then go on eBay and search for "Omega 684", "Omega 684 movement", etc..
As for "Post Farming", this is more nuanced and ultimately subjective. It is going to be a combination of how much you are posting, and what you are posting. If you are making 5 or 6 new posts in one day, and some of repeating information from each other, it beings to become spam-like, and can be read as "post farming"
Sounds like you have great enthusiasm for Omega Watches, so don't loose it while getting to know the Forum and its rules. Try to pace out your new Posts.