If the cab is efi already, it's dead easy!!!! If so, you can use your own loom, but you will need the ecu and map sensor (make sure they are both the same type, ofab/ofac) you can tell this by the map sensor, if it's flat and black it's ofac, if it looks like a cossie one(webber) it's ofab!!) So really you want the one for your type of loom!! You can use your box if you want.
Any turbo radiator/ intercooler combi will fit with a bit of wigglin about!! The only prob is the exhaust down pipe in fact you really need to go the t3 route straight away as that saves a lot of hassle, just make sure you make a heat shield for the crank sensor. The rest of it is just making intercooler and coolant pipes fit!!