To my knowledge, Busaru, Small Cars Performance and Van Cafe offer solutions for this aspect of your project.
Mick Longley from Busaru published a very helpful series of YouTube video if you ever decide to make your own wiring system. I am actually working on this aspect of my project for a 2011 EJ25 and it is not that bad, I should say fun and a bit challenging. Take a look to Busaru web site, there is plenty of good informations there. Also, I would say that the work to complete a EZ30 wiring harness is probably very similar has what is needed for EJ20 or EJ25, same rules to follow, same logic.
Bernard
Bernard Baril