i can tell you what i did to hardwire my valentine in my 04 titan.
i took the fuse adapter that they give you and cut a piece out of it so it would fit in one of my fuse slots.
i found a fuse that my truck didnt need but powered anyways. for me it was the heated seating fuse... i dont have the heated seating so it was perfect.
i took the fuse out and stored it and slid the trimmed metal plate in.
i took off the handle on the a-pillar and then removed the plastic cover it anchored down. i ran my non curled cord, that came with the valentine, down the hole in the side of the dash there because it goes right to the fuse box.
i plugged it into the fuse adapter and ran the other end up along the a-pillar so that when i put the plastic cover back on you wouldnt see it. then i stuffed it just inside the carpeted roof cover at the windshield. you can just pull that back and stick it in there because the cord is small enough to fit there. there is a finger slot in the very middle of it above the windshield by your mirror. use that to pull it down enough to slide the cord in.
i made sure that the extra cord was wrapped up and i put it behind the dash in that hole between the a-pillar and fuse box.
all together it took me about 3 or 4 minutes to do.
the hardest part was getting that folded cord to fall straight down the space to grab it by the fuse box.
i hope this isnt too late to help you because reading what you were going to do sounded difficult.
