From my experience, the ECM's for Foxbody are no longer available from parts stores. You can by used from Ebay but they are getting pricey, in the $300 to $400 range. And if you buy used you might get one that's not all good. It looks like the best way to approach the bad ECM issues to either try and repair them yourself, or, ship them off to a vendor which either swaps you with a replacement or repairs yours and returns it to you.
I had some recent issues with my ECM on my 92. It wouldn't start and the pump prime ran continuously. It's capacitors were bad. You could clearly see that upon visual inspection. I replaced them myself and I think I did a clean job of it. However, it did not solve the problem so I assume there was additional things wrong with that ECM, or maybe one of the replacement capacitors were bad. Anyway, I sent it to a vendor and they sent me a replacement which solved the problem. Cost about $100
I have a thread of my own on this issue somewhere on here and I plan to update it. I'm waiting for the delivery of another ECM which is for my 93 vert. That car was running fine but I figured I would visually inspect the ECM caps. They were leaking, corroded and one had a broken leg. Clearly, that ECM would have eventually failed, probably sooner rather than later. Considering you cant just go to the parts store and grab a replacement anymore, a failed ECM can leave you stranded and in need of a tow truck. Not something I want happening when I'm 150 miles from home on a weekend road trip. Not only am I refreshing the ECM's in both cars, I'm also planning on refreshing a spare ECM that I have. It will be carried along on longer trips.