Bearings are not suppose to be perfectly round. Your clearances should be slightly more at the parting lines. This is to allow for a better hydrodynamic wedge [oil] to lube the entire bearing. It is also to allow for slight distortion when the main caps deflect. If the bearing were "round" the parting lines would pinch the journal and scrape the oil off which would allow the journal to grab the bearing...instant spun bearing. As for your clearances they should be ok for the smaller journal of the Chevy and the rpm limit of a jetboat but IMO they are on the low side. If it were a Ford with bigger mains I prefer something in the area of .0032" to .004" depending on use and rpm the engine will see.