Turn a small drill press into a Bore/ Hone. Bolt it to the top of your engine block & do your own machining .

Hairline crack in the cylinder? Or something else? Elaborate. Anyone ever see a hairline crack in just one cylinder that can't be seen when it's magniflux , with the naked eye?
So, you're saying you paid to have the block Magnafluxed? l Sounds like an odd thing to do when you're convinced that it was a "cheap as gasket" that didn't get torqued correctly. More money wasted that could have been spent to do the job right. Or just more breath wasted on a subject that is totally inspired by overindulgence in a particular type of mushroom.