At my previous job, we bought a "reman" long block from a facility in the Dallas area, engine looked really good (visually) from the outside. I prepped the engine and installed it.
When I fired it up, noticed it had extremely low oil pressure, pulled the pan back off, rechecked the pump, pickup, really couldn't find anything wrong. Pulled the engine back out, put it on a stand and started disassembly.
Come to find out, some of the rod journals had been turned . 010, some were still standard but under minimum spec. Pulled the crank and had it turned properly. While waiting on the crank, I could tell that some of the cylinder walls looked fresh and some didn't. Pulled one head and found two standard bore holes, one . 040 hole and one . 060 hole. Pulled the other head and found pretty much the same thing!!!. .
You might inquire what brand of parts they use for rebuild, exactly what the block is spec'ed out at, the crankshaft, What machining processes they use... . etc... If they check/correct line bore. . If you get vauge responses to any of your questions, I would shy away from them. . Any engine can be reliably rebuilt, usually better that factory if the right procedures are taken.