If you're going bespoke with the wiring like adding extra gauges etc then you could use a neat box of tricks sold by Car Builder Solutions (CBS). They sell a module with all the relays, correctly rated fuses and flasher unit, all you do is attach the components and switches with the right thickness wire.
I'm using one in my Mk1 Cortina build which originally didn't have a single fuse anywhere in the car which frankly sounds like a fire waiting to happen to me.
http://www.cbsonline.co.uk/product/CBS_12_Circuit_Wiring_Module_WRMOD