I have a survivor 1969 427 4 speed,fully (all options) factory equipped all original even down to the original spare tire and rim never removed from the car. I was the first person to remove the T top, it was garage kept for 34 years, I do know a little about value, mine is 100% documented which makes it rare and upper end.
Anyway a 350 like the one your looking at in very good condition with the options offered would go for about $22,000 or less if an automatic, the (Maco) was made for several years but the 69 was the last year for the uni body construction. If you go to the big block, they made the single carb 427 and a Tri power 427 also a 454 the problem with those 2 is they have solid lifters and a pain to keep adjusted, they do go for a little more then mine because there are fewer of them. The 350 engine is nothing special and used a lot for daily driving same look just a lot of them around.