I have a 4.2 with a 4.0 head and renix setup, would i get much benifit from one of the bored out throttle bodies, and which one would work best, i have found 58mm and 59.5mm the stock is 52mm i beleive, i was also looking at maybe installing some ford 19# injectors, what kind of ill effects can i expect or things to steer clear from. Thanks  

If you feel you must upsize use the smaller of the two. Like bigger carbs, too big can reduce low end and mid range response due to lower mixture velocity in bores and less complete mixing of fuel and air. On injector size, this is not a diesel and a bigger injector than you need is wasted money. The only time you really need a bigger injector is when you run NOx with a dry shot and need more fuel or you run forced induction.  

I was just wondering because, of having a 4.0 intake system on a bigger displacement block if it might be starving or not getting its full potential.