you'll need the 2.8 capri xmember and drivers mount - that mount will bolt straight up - the passengers wont (u could use the 2.8i pass mount but u will have to make an adaptor plate.
also prob the best way to go gearbox wise is a T5 - but youll need a bellhousing from a 4 speed 2.8 mustang.
also, all of the overhead cam 4 ltrs were autos - youll need a flywheel and clutch off the earlier 4.0 exploder if u go SOHC.
You'll need a sump off a sierra - the exploder sump wont fit - the sierra one suits the capri but the exploder 4.0 block is wider so u will have to make slight mods to the sierra aluminium sump to make it work.
also the oilfilter arm will need work (or use a smaller filter)
I would go with the earlier 4.0 manual non SOHC engine
they will catch u on emissions - unless u go LPG