... We target our Mains to be less than .0005" Straight & Round, Yes, even on Cast Iron Stock Blocks.... for "our" comfort zone.
Align Honing is one of the most difficult Machining Operations to do well.
The main bore on a 383 is 2.8175 +.0005 -.0000. So .0005 is all you get on bearing bores typically to be in spec. This you can measure yourself, if you have a good feel, with a dial bore gage. The best way to check alignment at home is how I described it above. It is a good functional check. You can also put a dial indicator on the center main journal to check the straightness of the crank. I don't machine anything unless it is out of spec.