Agreed with the above post.

If we are talking about an older Mopar ANY large current load you add to the system is going to increase the output of the Alternator and then add considerable stress to two bulkhead connectors (four small copper connectors) no matter what side you tap into. You can add all the junction blocks you want but I can show you photos of what my wiring harness and dash looked like when the previous owner burned it up.

This photo is a little confusing but it shows the flow of power. The default load point in these cars is currently the weld-point under the dash near the ammeter. What you probably want to do is first MOVE that default load point somewhere under the hood. If you add an Alternator bypass wire between the Alternator and the Battery you can use the Starter Relay lug as a central point to pull power. This will let you add relays or tap into the system for power without stressing the bulkhead.