A lot depends when the castings were actually made as to whether they can be rescued or not, as ST have been through a few sets of hands over the last few years, and I am positive that some of the intermediate owners were actually using castings for patterns rather than the standard oversized patterns that allows for metal shrinkage.
This started to show up about 5 years ago, people were finding that they couldn't fit the castings together as some were too small and the fixing holes actually came over the edges of the castings if drilled to the plans.
At the time, the only helpful saying that ST came up with was that these are made for model engineers to build, and their knowledge should be able to solve any problems that occur.
I am hoping now that ST is under better ownership and takes this problem by the scruff of the neck. Unfortunately, until that happens, there are hundreds, if not thousands of theses smaller castings out there.
That is one of the reasons I say a beginner to this hobby shouldn't start off with casting sets, especially ST ones, as they wouldn't be able to cope with the problems that arise, and I am sure that is one of the reasons so many of these part built kits ended up under a bench somewhere, and only surface again when all the problems have been forgotten about, and sold on places such as eBay to unsuspecting buyers.
You should be safe if you buy an obscure kit to build, as they would still have the original, many years old casting sets, or they still have unworn wooden patterns, but very popular ones might contain the smaller castings until this new owner sorts them out, if they have not done so already.
John