Haynes Manual Doesn’t Have 8 1/4 ???

Geezus. It's pretty simple. Don't use Haynes

Wander over to MyMopar and download a free service manual, you don't have to sign up or join or do anything. Many years available, and loads more information than Haynes ever thought of

MyMopar

You may have to settle for Dodge vs Plymouth for a correct year, etc

Service Manuals – MyMopar