I agree on the heat part. It is probably the best and most likely method to work. The glass transition temp is probably in the 130°C ball park.
If that fails, long time soaking in a paint remover for epoxy paints may soften the epoxy enough to allow you to chip it out. You will probably have to repeat that treatment many times. Let it dry between treatments, scrape, then repeat. It is a messy process. I don't know of anything that will dissolve epoxy like lacquer thinner does to lacquer.
Any even more messy process would be to use the nitric acid. Iron is reasonably stable to pure nitric acid (i.e., in the absence of water), but the amines and amides in most epoxies are destroyed. I have used nitric acid a lot in my life for other purposes, so let me emphasize that I would not even try that approach here, unless I was truly desperate for the part.
BTW, neat nitric acid is a great way to remove galvanize coatings in a controlled manner from small steel parts prior to soldering -- like the ends of pushrods used in models.
John