Review this thread and this thread. Much of it is for a 2.6, but is still applicable.

Basically, a lower t-stat, hood louvers, extra cooling fans, etc, are all well and good, but they are just band-aids on an underlying problem. Yes, I have all of those, but since my cooling system is in good working order, they allow my engine to run extra cool under harsh conditions (such as low-speed crawling on a hot day). Look through these threads to see what may be of issue.

A lower t-stat won't keep you from overheating. It basically may let your engine run cooler under normal conditions or may allow you more time to catch an overheat sooner, but if you t-stat opens, it just opens. It won't keep the heat from climbing if something is amiss with your cooling system.