If you can get McK slides easily, you are not going to look for them any more very soon. Having said this, you may find MGI reports that are some time in McK format; enough to give you an idea.
MCK is a standard format to convert between, in theory that means if you are an MCK specialist, and you want to go after MAST, the reports from MCK (if they even exist) have MCK metadata. So if you are going to have an MAST database anyway, an MAST DB will be even more valuable as it will probably include the MCK reports. How to get the database MCK reports on MCK documents are usually quite scarce. You can usually get them for a small fee — I paid 300 a year ago for a good number of MAST reports. They are also often available on the site which you are trying to scrape your data from but if you really want to get a better idea of the data and a quick database, be prepared to spend a lot of money. If you think you have a good idea, you can.