I have had 2 engines built by local shops. I had visited 2 other shops, 1 was very small and dirty. I saw no clean assy room. Pricing was typical of the other 2 I visited. The 2nd was very busy, I was given a generic sheet with pricing info. Costs of teardown, cleaning, inspection, machine work etc. the guy didnt have time to talk. The 3rd shop was a recommended shop. The shop manager was extremely friendly and had all kinds of time to discuss the build. I asked about turnaround time, was given a non comittal time frame. As I was just begining the full body off I wasnt too concerned. I told him to take his time and do it right. We discussed decking the block and my desire to retain the original engine pad stamping. No problem, they can adjust the machine to leave the pad untouched, I was told. Ok, price was reasonable, in line with the other 2.
I took the engine fully disassembled to him around the 4th of July. I didnt get it back until late Jan. Despite my leaving him alone for the first 3 months, I started calling around late Oct. then 3-4 weeks later, then when I visited the shop in mid Dec, he pointed to the block and said yours is over there. Numbers milled off. Not happy. I left in disgust. I was called in late Jan that it was ready. The engine had problems from the begining. It blew coolant overboard, 72 manuals with ac have no coolant reservoirs. I would adjust the level, but still, it blew over. I never saw over 200' temps. Remember old Jim Ward? He said u have issues. I never imagined that the issue would turn out to be a cracked cylinder wall! At only 2000 miles on the build, the block was trash.
My new engine was also built by a local. He told me new blocks are the way to go. Darts shp being a reasonable choice. If I decided to go LS, he said to buy a gm crate engine. It was a great deal with warranty. I like the sbc, they belong in a corvette. Everything is new, as I upgraded quite a bit, 434 cu in. At barely 200 miles, the engine is what I should have had the first time. Big block power in a smaller package. Build time was still 3 1/2 months. He too is busy. Time will tell, but so far, Im pretty happy.
I guess it can happen, the missed crack in the cyl wall, I guess mistakes can be made in milling off important numbers, I guess build times can be long. But I know I could never recommend that particular shop to anyone.
Sorry for the long post, had to get it off my chest.

 

Write on their contract if numbers are not left intact,
machine shop pays a penalty of x $ amount.
to a machine shop oprator your numbers are nothing. ...opps sorry !
to a numbers matching corvette owner they mean $ Value.
Protect yourself from idiots.