I've been looking at these trailing arm braces and anti-hop bars and I am not sure where they go or if they are difficult to install. Help?
The braces are more for strength/safety. They connect the front mounting point of the lower to the front mounting point of the upper control arm to reduce flex, mostly in the upper control arm mounting points on the crossmember. Some GTO's had similar connectors from the factory, as GM recognized this as a potential problem area.
The hop stop bars essentially relocate the rear mounting point of the upper control arms "higher" to change the angle they make, resulting in moving the suspension instant center towards the rear of the car. Supposedly this helps control wheel hop (are you experiencing wheel hop?) but it also negatively affects the leverage that's used to "plant" the tires on a hard launch. Wheel hop can also be caused by any combination of loose/worn suspension bushings, weak shocks, or incorrect pinion angle. Speaking of pinion angle, moving the suspension mounting points around is an opportunity to disturb it, leading to driveshaft vibrations and other problems, so be careful and make sure you measure your pinion angle both before and after installing these, if you do.
Of the two jobs, putting on the hop stop bars will be the most difficult because if the location. If you leave the rear end in the car, make sure to do them one at a time if you can, always having at least one upper control arm (and both lowers) fully connected at all times. Otherwise the rear end housing is bound to rotate on you some and you'll have to use some kind of leverage to get it back into position. You'll want to support the car by the axle so that the suspension stays compressed. If you support it by the frame and let the suspension 'droop', you'll find it difficult to get the upper control arm ends loose because the geometry of everything tends to try to twist the ends of the arms at the bushings putting them in a bind. If you choose to remove the rear end (which makes installing the arms easier) then you'll have to deal with disconnecting brake cables, brake lines, bleeding brakes, using multiple jacks and a helper or two to get things lined up again so you can install the bolts... There are advantages and disadvantages to both methods. It's not all that hard, really, if you take your time - but if you've never done something like this before I'd plan on it taking a full Saturday at least.
So, the braces are probably a good idea and they aren't all that hard to install. The hop stop bars, eh... I'd consider them only if I was experiencing bad wheel hop on launch and had tried everything else to correct it first.
But that's just me.