I have two plugs in my dash, one a usb the other a flat accessory plug, no power
This will likely help you, see this link, http://ae64.com/Legacy_Gen4_HU_Transplant.htm And, if my answer helped you, please mark this best answer, thanks.
Read through all the details and it will explain all of the options for connections. Good luck.
Looking for a Used Outback in your area?
CarGurus has 26,290 nationwide Outback listings starting at $1,000.
Search Subaru Outback Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Subaru Outback Experts