He's big but did not medal in any high level amateur tournament. Could be a top 25-50 type of talent today. Anything better than that will take lots of improvement over what I have seen.
Hard to know what to expect of him, but he is pretty young at 25 and heavyweights dont mature till later than that. I think he could be built into a bit of an attraction at the very least anyways.
Some footage of Sheehan from some years back. Sheehan in red. https://www.youtube.com/watch?v=Zwm-j***ak0 https://www.youtube.com/watch?v=AEM9GXcu1Os https://www.youtube.com/watch?v=vzw4jdhgvic