it's actually easier to fit them using the 4wd setup than the 2wd stuff as you need to bugger about with gearboxes whereas fitting them to a 4wd set up all you need to do is source a 2.9 xr4x4 sierra and transfer the bits over

if you want to go the 2wd route you need to source a 2wd dohc 2.0 sierra as well to get the back of the gearbox off of and the cradle etc