340 crate motor

they had replacement blocks had a 340 replace the 273 4bbl in my 68 GT convertable back in 1969
I'm sure they had replacement blocks for warranty purposes along with any other parts that failed. What I'm referring to is after these parts including engine components are depleted they become obsolete. As far as I know after this time frame passed Chrysler didn't start reproducing 340 engines. Again I maybe wrong but by the mid 1980's I was not able to purchase one from a dealer here in Canada unlike what GM offered at that time.