There was never a SM produced for the 620/630. The substitute would be the 60 which is fairly different, or the 720 which is also pretty different.
I'm totally agree that a guy needs a set of manuals for every piece of equipment that he owns, but in this instant it is not possible.
The only way this info could be gathered would be from service bulletins. You can't get those @ 800-522-7448.
Btw. The quality of Deere manuals leaves much to be desired. The paper is thin, printing is smudged and the price is silly. Why not suggest these two cylinder and new gen guys to buy their manuals from an aftermarket place that actually strives for quality? Some how these aftermarket folks are able to make clearly printed manuals on thick paper for half the cost of Deere. It's a no-brainer.