I had Marine go through my 3.0L SC crank years ago and David Eden was a great guy in the process. No nonsense and extremely knowledgeable.
Marine cross-drilled it, plasma nitrided, straightened and polished the journals, balanced it (because I had it lightened- not necessary and probably not recommended by most) and tapped all the plug holes for set screws to make it easier to clean in the future.
Yes the #4 main bearing is grooved and some will say grooving the bearing is better. I figure if the #1 main journal is grooved originally, probably not the end of the world if the #4 is grooved.
If shipping wasn't so expensive and sketchy nowadays, i'd send Marine another one for my 3.2L rebuild. I believe Marine is the company who, last I heard years ago, manufactures Henry's Supercranks?