Hey dude.
Nice purchase, I'll be following your thread if you decide to do it up. The 4WD vans will never be ultimate off-road performers because of their design; like others have said, ultimately they're limited by their angles and whenever you see a modified one under-body bash protection (particularly at the front) seems to be a pretty big feature. Having said that though as for a vehicle that will get you out and about to see this great country of ours without having to stop where the tarmac ends, cart all your gear around and provide you with a place to kip, you couldn't do much better.
If yours is a part time 4WD it won't have a center differential, it'll have a transfer case. I have no idea which type but I'd guess the good folks at Toyota probably raided the Hilux parts bin for it rather than anything else.
There's tons of van sites out there with a heap of good design ideas for the interior; from camper layouts with folding everything to hippy-mobiles with shag carpet and disco-balls. There's also a Facebook group for Hiace Super Custom fans if you're into Facebook:
https://www.facebook.com/pages/HIACE-SU ... 5514383497LIke Zed said above; throw enough money at it and anythings possible... Have a search around the net and on some of the overseas 4WD forums and you'll probably be able to find out how much they can be raised to obtain clearance to fit larger tyres before you have to start spending silly money.
Have fun and once you start getting 'out dere, doin it' or modifying it keep the pictures rolling...