After the original tang safety Model 77, Ruger came out with the Mark II which had the three position safety and the long, non-rotating extractor but was still push feed. There was a slight lip which went all the way around the bolt face so the round had to be chambered and then the extractor snapped over it.
After a while they ground off the bottom of that lip and made it a true CRF, then later came out with the Hawkeye series which had a different stock design and different trigger.
The main thing to look out for with the original Model 77's is that they were made during Ruger's cheap barrel period, you could get a good one or it could be total crap.* Sometime around the 90's Ruger began producing their own barrels which were and still are good to very good.
All this IIRC.
* Friend of mine in the mid-70's had a standard Sporter model .220 Swift that was decently accurate by the standards of the day, at least it would put five shots into an inch or just under. Later on in the early-mid 80's I had a heavy barrel tang safety "Varmint" model 25-06 that wouldn't group anything into less than 2" and most loads into around 3". Very frustrating rifle that went down the road to a guy who just wanted to shoot deer in his back yard with it, a task for which it was well suited.
