I have line bore and line honed thousands of 350 block over the years and unless we are putting on a billet rear cap I have never touched the seal area. 400 blocks are a different story!! I have never in 38 years of building engines ever offset the rear seal in a block before.
Ooooops, I am wrong, sorry... I was thinking of 400 blocks, my bad...
I have a Dart Little M 400 main block that was lined bored, and I had to use a special undersize seal because of the line bore. Mine is a 388 using a 3.625 stroke with 4.125 bore and 6" rods, so I guess when i read 383 I was thinking 400 block mains...?