Minimum wall thickness for cylinder walls

[LDM]

Well I finally managed to get my old block torn down and just finished sonic checking the cylinder walls. Most areas were above the .300", although I did have some areas that were .250" and on the 4-6 and 5-7 inside walls it was as low as .175" in a few spots. This is above the .135" minimum I've seen for most recommendations, although it would be close after a .030" bore to build the 383 stroker. Anyone have any further info on whether I should get a new block or this one would be good? I plan on some high HP/TQ with nitrous on the this build and would rather be on the safe side.

Also, should I be using regular cast iron or nodular cast iron on my sonic checker? I didn't see a huge difference between the 2 when I tested it on one of the cylinder but I also wasn't able to find the specific type the LT1 cylinder walls are made of. If nodular I will go back over each bore using that setting instead, see if I get thicker results.