Questions on customizations

[Pinchecharlie]

So I am hel@ bent on doing a smooth firewall and running as much of my lines/wires under my inner fenders and or trying to hide them. I feel in love with "Sanford and sons" build and even though its beyond my skill level I am gonna try. So here's the dumb questions
What do I cover the interior firewall with if I have no little black fastener things?
Do I weld fasteners inside?
Can a guy glue on headliner material or carpet?
Same with inner fenders, should I weld some kind of wire clips or straps to hold the lines?
Which ones would work best you think?
I started welding all that up and realized I didn't really know what I was doing lol!
If you have any tips or experience doing it that would help me out I'd appreciate it. Thanks charlie