[84LX89GT]

Typically through the years the HO 5.0L engines had Double Roller timing chains as opposed to the silent gear type, The 351W engine firing order (early models basically had the 351 camshaft because of increased lift/duration), Stock headers in the mid 80's up, higher flowing intake manifold, HO's had forged pistons from the mid 80's until '92) and '87 up they had the E7TE heads like the trucks that flowed better than the passanger "high swirl" E6TE heads (E6TE used in mustangs in '86). Also, in the early-mid 80's the HO's had serpentine belt driven accesories with a reverse rotation water pump as opposed to standard belts and rotation water pump. The HO's also always had higher flowing air filter housings. Also the HO's got a roller camshaft in '86 whereas the regular line i believe (not absolutely certain held on until later). The crankshaft is the same as other models, just a regular cast crankshaft and the rods are the same as well. A double sump pan was used for crossmember clearance.
I believe this just about covers the basics