Yeah something in the range of .030" - .050" larger HG bore than cyl bore, is the norm. That puts the HG half that far outside of the cyl. To put that into perspective, a standard business card is about .016" thick; so that's roughly the gap you'd have, all the way around, more or less.

One reason for that is, the machine work (cyl bore location, dowel pin location, etc.) isn't "perfect"; there's a fair amount of tolerance in all of those. ALL of it, however much it is and in whatever direction(s), will appear in the fit of the HGs to the block. It's not possible to have them "real close", without a pretty good core to start out with, and some serious attention to detail.

I'd agree, a 4.1" HG on a 3.78" bore is kinda excessive. That's roughly 10 times the "standard" fit.

 

If you're going boosted or nitrous the LS9 is a good choice.
For N/A make sure you can get an acceptable quench.

 

 

Oh god. It even has a watermark.

One of the best scenes in cinematic history.