You have some good advice here. Crate motors are built for a car that will experience full throttle for seconds at a time. Marine engines are under heavy load for hours at a time. Odds are high the engines will not live for all the reasons listed on the posts.

I understand this with tolerances on large BBs with cast iron blocks.
What about the LS3-6.2, which has an aluminum block and 80 hp/liter, close cooling sistem? Is it also dangerous to leave automotive tolerances there between the piston and the cylinder?
So far I have done about 200 hours, of which about 15% wot-6,000 rpm, the rest mostly at 4,500 to 5,000 rpm, but a reall comment from the "old saylors" on this forum would be very welcome.

Engines are prescribed beating tolerances. Marine engines, specifically the harder working specimens, need to be on the larger side of those tolerances.

Purpose build high performance marine engines pretty much need to be on their bearing specs.

Your 4500-5000 rpm is on the high end of a cruise rpm. Hard to say how your bearings are making out. You never really know unless you open them up and check/adjust etc. That is the point.

For what is supposed to be a hand built GM crate engine, I would expect a build sheet with bearing clearances.

If it lived 200hrs so far, I would think you are good.

Cut the oil filter open(if you haven't) and check if there is any metal on the next change.

I have to apologize.
The total is a little over 20 hours plus cca 10-15 hours slow drive and not 200 hours. I will look at what is in the cpu memory.