I put the crossover box behind the door cards and ran a relatively thin speaker wire from there back through the rubber tube carrying the wiring loom to the doors. There's a very small clearance between the rubber and the multi-way electrical plugs. I started on top of the dash and fed the wires down past the foam that fills the gap between the dash and the quarterlight trim. I lost a bit of skin getting the wires through, but it wasn't hard.
how did you put the tweeters on the dash?
The tweeters sit in pods that came with the set and are in the far corners next to the A pillars. You could screw them in place, but I used little pieces of double sided sticky foam tape.
A more ambitious (and better) solution would be to mount them in the A pillars after moding the trim panels with fibreglass and recovering with cloth.