Value of 1969 340?

Not so fast...340's are "hysterical" and there are those that want a classic.
But lots of guys don't care about that and won't pay extra to get one.

Well said save them for restoration's @ if you need an engine for cubic inches pluck a good early model 360 and build it !!
A 360 is like a 318 [ Not Mythical ] just a motor that will suit most needs.