Wiring loom question

So it's got to a point where I need to rip out all the crappy electrics in my swb pickup and start again before the thing bursts into flames.
It's an 1983 88" which was originally a diesel (I think) which has had a 3.9 v8 dropped in running su carbs.
Fuel pump, fan, fog lights, spot lights, all Run from additional switches in dash,
The original ignition isn't used as a separate one has been fitted for some reason.
So my question is......should I get an original diesel series 3 wiring loom and modify it, or buy a load of cable and start from scratch. (this will be my first ever re-wire)
Any advice greatly appreciated .

get a std to service the car and but fan, fog lights ,pump etc on purpose made loom /fuse box,run seperate feed from starter or battery for this

Nice one, thanks for the advice, can anyone recommend a good supplier for a loom?? And do I need a specific one?

Autosparks, World leading supplier of classic car wiring looms
looms aren't cheap but these guys sell loads of good stuff