It'll be a lot more than just the front Xmember.
It'll also be the cross members in the middle as the rear tailshaft output is in different location, and the one under the one under the gearbox is also different as the exhaust has to fit between the Xmember, the propshaft, the fat gearbox and the chassis rail. It'll also need the floor, the seatbox, the firewall, the bonnet and the facia, modified to fit the engine in as they are all a lot bigger than the 4 bangers parts. The guards also to relocate the headlights otherwise they will hit the radiator.
I've been down this path, and to be honest I wouldn't bother with a SWB - I had to push it out to 100" to make it work, and if you're doing it to a LWB then it is a far far better proposition to just buy a Stage 1 where the factory have done it for you with all of the good parts in the driveline and in the chassis.
