You've just bought one of the most bomb-able motors, IMO
I and many others have the SO motor, About 199. 6hp mine did on the dyno when stock. Now with TST,EZ,Injectors,CP3 mod - about 600hp all day long
Congrats on the truck!!!
Opps- almost forgot to answer your question... Upgrade fully to the HO spec? nope, too expensive to change with the little stuff like j-jets for oiling. But you will be able to make way more HP than the stock HO - So dont worry about being 55hp down
HECK, the smarty actually starts from an HO setting, SOOO, the S. O. motors actually gain 50hp more than HO motors with the smarty (i heard)