Full wiring harness replacement advice

[DZP]

Hi,
My 72 Stag has suffered the "melted wires in the fascia harness problem" caused by fitment of electronic ignition and incorrect wiring of the Tacho. I see others have experienced this. I am going to replace the fascia harness, but was wondering how much of job it is to replace the main harness on a fully trimmed vehicle.
Is it feasible to replace the main harness with engine, gearbox and all trim fitted?
Are there issues passing the harnesses though wings/sills etc?
I will purchase the harnesses from Autosparks.
Thanks.

[new to this]

The hardest part will be where the wires go across the heater,you're have to take the heater out of the car,the rest is straight forward

Dave

[TR5convalescent]

If you’re going to Autosparks think about any extra items you want like fog lights, electric fans radios and sub woofers. They will incorporate these for you at very reasonable cost and colour code them too.

[DZP]

I found that some of the ignition feed wires in the main harness were also melted. I have ordered main harness, relay board, centre console and fascia harness from Autosparks. Following previous advice (above) I am also having some extra wires inserted into the main harness to support some accessories. So, in a few weeks time the real fun begins.
Can anyone tell me if there should be a cover on the relay panel?
It looks like it is designed to accept a cover and is rather exposed without one.
Thanks.

[malc4d]

The parcel shelf covers the relay board