I have been searching and have not found exactly what I believe I need.

Scenario: I am adding LED's to my truck
1st input is from a dashboard on/off switch
2nd input is from a signal from my courtesy lights

If either is charged the LED's should be activated. There are 12 LED's at 9 Watts each so estimated 10 Amp draw.

Question: What is the proper safe way of doing this?

I am thinking two relays, but looking for expert advice and possibly a schematic with the SPDT relay. Your help/advice is greatly appreciated.

 

Use a SPST switch and a 12V automotive relay (assuming the courtesy light switch is not adequate to handle the extra 10A).

Connect 12V to one of the relay contacts and the LEDs to the other.
Connect the LED relay coil to the courtesy lights
Connect 12V to one switch terminal, and the LEDs to the other switch terminal.
That way the LEDs are on when either the courtesy lights are on, the switch is on, or both.

Alternately if you don't want the dash switch to pass the high LED current so you can use smaller switch wire, use a DPDT switch and connect as follows:
Connect the relay contacts to the LEDs and 12V.
Connect the switch wiper (center) contact to the relay coil.
Connect the switch ON contact to 12V.
Connect the switch OFF contact to the courtesy lights.
Again the LEDs will be on for the switch, the courtesy lights, or both.

 

Thank you for the quick response, honestly didn't expect that

Something I may have missed is that when I walk up to my truck it detects the key and my courtesy lights turn on.
With that I want to be able to have this also activate my added LED's regardless of the switch position this is why I was thinking I may need 2 relays.
I like your second option above using the DPDT, however if the switch is off (middle) or on the 12V, I suspect walking up to the truck will not activate my LED's off of the courtesy signal as the DPDT is not in the position of the courtesy light signal?

 

I want to be able to have this also activate my added LED's regardless of the switch position

Both of my solutions will do that.

however if the switch is off (middle)

The DPDT I would use has no center off.
Both switches have one position (dome lights will activate LEDs) or the other (LEDs on).
I don't see that it needs an "off" position.