Stop in for a cup of coffee
But now after reading the posts from guys who have had seen many original examples, I'm going with them. In fact I just cut and pasted from four of those posts. The first two quotes sum it up clearly.
Alaskan_TA
The X heads were used into the 1970 model year, but not for all of the 1970 model year.
There are plenty of 1970 340s out there with 915 heads.
Cylinder Head ID - Casting and Date Code
Cracked Back
If an X headed 340 made it to 1971 production it's one in a million.
915 J heads were the primary head in 1970. The X heads ran early in production for 1970 and I've seen some December 1969 build cars with them, but they are not the norm.
1971 plymouth 340
Mopar Official
Brian6pac Cylinder Head ID - Casting and Date Code
Jarahabi Small Block Heads
I'm willing to call the books wrong on this.
My books too.
But now after reading the posts from guys who have had seen many original examples, I'm going with them. In fact I just cut and pasted from four of those posts. The first two quotes sum it up clearly.
Alaskan_TA
The X heads were used into the 1970 model year, but not for all of the 1970 model year.
There are plenty of 1970 340s out there with 915 heads.
Cylinder Head ID - Casting and Date Code
Cracked Back
If an X headed 340 made it to 1971 production it's one in a million.
915 J heads were the primary head in 1970. The X heads ran early in production for 1970 and I've seen some December 1969 build cars with them, but they are not the norm.
1971 plymouth 340
Mopar Official
Brian6pac Cylinder Head ID - Casting and Date Code
Jarahabi Small Block Heads
I'm willing to call the books wrong on this.