Do you need the engine or the accessory parts like inlet, carb, alternator etc. too?

Engine in XR3, XR3i MFI (XR2i/3i EFI apart from the head) were nearly the same and can be used to replace the XR2 MK2 engine. Also any other 1.6 CVH unit, just make sure it's got the correct CR and fit a XR or aftermarket camshaft.