i think engine bay is identical except engine mounts. because basically honda designed the 6gen platform to equip v6 and i4 engines. it makes sense for them to just make the chassis same and do little modification to each i4 and v6 because it saves manufacturing costs.
also, if you compare two cars, you can see that i4 has shizload of empty space in the engine bay. inside dimension is same as well as exterior dimension.
my guess is that in order to do j32, you would have to pretty much take everything out (engine,battery, fluid reservoirs, etc) and just straight up replace with v6 stuffs.
good luck, i'm predicting it will be at least $5000 project.