I think they are both large dates. The coin on the left, I can't see the curve of the 9 very well, but the height of the 7 looks large date. The coin on the right is definitely a large date. It's cool you are finding some 1970 S's. I hardly ever see one and have never found a small date!
The best way to find a 70-S SD might be looking at mint sets on ebay or at dealers. If you look at a bunch of sets you'll find a SD or an RPM-1. Also, look at dealers flips because they cut up a lot of 70 mint sets for the 70-D halves (only in mint sets) and the cents might get put in flips as singles.
These small/large dates including the 60 and 74 can be tough... At least on the 82s the 2s are completely different... Don't remember if I gave you a link to this before so here it is... Some excellent diagnostics there on the LCR -
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