Well D,
Welcome aboard! The decals are available aftermarket from a few suppliers of Mustang parts (NPD and FMR for example).
Document as you would have done your others with photos and then try to replicate the rest. Most of the paint markings have been replaced with serialized part numbers on most components if that's what you are talking about. Others can join in on this as I'm new to this stuff too.
Looking forward to seeing your car done!
