Stereo install in '79 F-150

Ok so I have my subs on order and just got an amp yesterday. I thought I would be able to get by with my old HU (some pioneer POS) but when i went to hook up my new door speakers I seen "wiring hell" going to the HU. I am goin to get a new one and start over, but I was wondering if anyone knew where i could find a 1979 F150 wiring diagram just in case I need it. Is it really that bad to hard wire or should I get a wiring harness that might work? I have to run a power wire for my amp anyway so i can run a constant to the battery for the HU to. Will a Walmart brand amp wiring kit with 8 gauge wires work for my Concept CD-1302 amp? It has 400 x 1 @ 4 ohms, Had to get that one cause of budget or should i go with a 4 gauge kit? My pioneer HU is a detachable face plate CD unit so i was wondering do I need the DIN type removal tools for that? Thanks again guys for all the info u have alrdy givin me. You all are great.

you can try these codes but they are for ford 86-95. I'll keep my eyes peeled for specifics.

Black Plug = Speaker Plug
: Wht/Grn = R frnt + : Grn/Org = R frnt - : Pnk/Blu = R rear + : Grn/Org = R rear -
: Org/Grn = L Frnt + : Blu/Wht = L frnt - : Pnk/Grn = L rear + : Pnk/Blu = L rear -
Grey Plug = Power Plug
: Yellow/Black = switched 12v : Grn/Yellow = constant 12v : Black = ground

Ive owned lots of fords and these sound right. use a test light to be sore though.