A 39 Plymouth has the same basic frame as the 46-48 Mopars. I've made motor mounts for at least 4 of these cars, but I don't think I ever took pictures. Basically set the engine where I wanted it, and built my brackets off the side frame rails that would attach to the rubber parts of the motor mount brackets on the engine. I might suggest you bolt on the exhaust headers or manifolds to be sure where you mount the motor clears everything.

You will need a rear sump oil pan.
If you offset the motor to the right (passenger side) 1 1/2" to 2", you will clear the steering column.
If you notch and box back in the front crossmember so it will Make sure you have enough clearance to put belts between the crossmember and the pulleys when your done).
You will want to modify the lower 6" of the firewall bump (a hammer will work) on the right side (passenger side) to give additional clearance for the head. Gene