FI conversion question for those who have done it

[Petersubaru]

I know one can run 12v from the key and other places to power items under the hood, which brings me to my question...is there a way and enough room under the hood so that all the wireing will not have to be rerouted back under the dash but kept under the hood including the ECU...I would still like to keep the option of reverting back to a carbed car rather easily