Hiems and TRE's are a personal preference, if your going to go with a hiem on the factory knuckles there are some things to look out for.
With a regular bolt (2A/2B) and a drilled hole there is a lot of slop between the bolt and the hole. No matter how tight you get that bolt it still wants to wallow back and forth in the hole on the knuckle. This wears the knuckle, wears the bolt, and potentially leads to the failure of the joint.... usually at the worst times.
Since the tooling and hardware needed to make a perfect machined fit is not always cost effective (or feasable), this is where we get cone washers and tapers (think a TRE.)
One way to take care of this problem is to mount a tab that the bolt goes through before it goes through the heim. This holds the top end of the bolt and prevents the bolt from acting like a lever (the fulcrum being the knuckle that was drilled.) This is called double sheer.
You could also use something like this... reason is because as you tighten the bottom nut it pulls the tapers tigher into the taper on the knuckle. This means that there is no slop for the bolt to wallow around. Makes a MUCH safer connection.
http://bcbroncos.com/store/product_info.php?products_id=770
Heim Joint Stud [47-31500] $18.00
I hope that helps, just don't want anyone getting hurt