Dodge started offering a V8 for the Dodge trucks in May of 1954. I happen to have a 54 Dodge truck factory service manual here. That manual listed repair info for two different Hemi V8 motors and two different flathead 6 motors. One Hemi motor listed was a 241 Hemi, and the other Hemi motor listed was a 331 Hemi. The only thing that make sense would be that Dodge offered both a Dodge version of the flathead 6 and the Dodge 241 Hemi, and may have had the longer version of the Chrysler flathead 6 and the larger displacement Chrysler 331 Hemi as options over either of the smaller Dodge motors.

I remember seeing or reading that Dodge also offered a poly V8 in the trucks as well as the Hemi, but the 54 service manual doesn't have repair info on a poly motor at all, but the poly may have been offered after 54.
Got nothing covering Dodge cars. Gene