The 2.9 is a good reliable car but spare parts are getting rare , you should hop on to the xroc forum https://www.xrstyle.co.uk/forums/
one or two things to be aware of is that the power steering rack is specific to the xr and not same as cosworth 4x4 or granada 4x4 . front hubs and drive shafts are also different to cosworth 4x4 . the rear diff is lsd but smaller than cosworth 4x4 . Look out for rust on the inner sills and front floors and also around the sunroof . Maintenance wise not too much to worry about other than grease front propshaft uj,s and regular oil changes . the mt75 gearbox needs speific oil https://www.opieoils.co.uk/p-147606-granville-mt-75-manual-transmission-fluid.aspx . If the car has ABS then it must work for the MOT so any warning lights relating to the brake system could mean replacement parts needed which will be difficult /expensive to scource good luck Dave