Dwight,
This what I found in the 70-71 Parts Book.

There is no listing for the 340-4 Barrel name plate in the May 70 edition of the 70 only Parts Book.

NAME PLATE, Hood,
1 - 3443 247 "340-4 Barrel"
2 - 2998 801 "383 Magnum"
2 - 2998 800 "426 Hemi"
2 - 2998 804 "440-6 Pack"
1 - 3462 491-2 "440"
1 - 3462 489 Lt. "426 Hemi"
1 - 3462 490 Rt. "426 Hemi"
3 - 9420 276 Nut