Hi Larry,
The first generation used the same diameter knobs, but a different style. In catalogs, the snare guards first appeared in 1973, which also shows the new strainer style, too. As for the guards, you just need to keep checking sites like eBay, or even post in the wanted section of this forum.
Check this link to see catalog pages of Slingerland snare drums. Just scroll down to the years you want to see.... http://vintagedrumguide.com/slingerland_catalog_pages.html
I looked through my Slingerland parts and found these parts that might work for you. They are from a Slingerland Yellow Jacket pedal. As you can see, one of the rods has been cut down, but still long enough to work with the SSK. The other rod has a bend, but, again, you can cut it down the desired length. You may also need to use a 10-24 die to put the threads higher up the rod. You can tap the existing holes to accommodate a 6-32 screw. The adjusting knobs can be installed so the flat portion faces the drum. These parts will at least get your SSK working. If you would like them, you can have them at no charge. You're in the States, correct? Just PM me with your complete name and address.
-Mark