The engine mounts will be your first hurdle. My mate and I made our own, took about 2 and half full days to set-up and fabricate the engine and gearbox mounts.
There will be no room for the brake booster, so factor in a pedal box set up.
The standard gauges won't work with the new technology, allow for some aftermarket ones.
The gearbox won't fit in a manual tunnel. If you not lucky enough to have an auto shell, allow for some fabrication work.
Custom exhaust and tailshaft.
To do it properly you will need to get an engineers certificate for the mods, so best start talking to one now. They will have requirements like keeping all the factory polution gear.
The more work you can do yourself (or get a mate to do for you) the less it will cost, allowing more money to be fed into upgraded brakes and suspension.