Yea - I am confused...are you trying to install a sub into your door? The L7 definitely will NOT fit in your 6.5" spot in the door
And the spacers are really the way to go. Depending on the depth of the ones you bought, you may need to get a thicker spacer, but it should work just fine.
And instead of cutting your harness, just buy the Metra adapters so you can leave the stock harnesses intact.