2002 to 2004 would be a direct swap except that the 2002 was the only year that had the oil level sensor so if you get a 2003/04 engine, you'd need to swap the oil pan. 2005 and up had changes to ignition coils and crank position reluctor. Whatever engine year you use, you have to keep your 2002 PCM. As far as internal mods, not much that can be done. Not even sure there's even any cams available for these engines. Have read somewhere online of someone that opened up the throttle body by porting it. You could get your PCM tuned during the time the truck is down, which is a quick and easy mod that yields modest results, mostly improved shifts.