First off, what wreck are you diving and whose boat are you using?
Having many a deep air dive under my belt, to depths far greater than your going, I would say that you can never train yourself out of narcosis- it's always there. I used to think I could after completing many a deep air dive with no problems and a roll full of good shots to show for my efforts, but ever since I started diving helium I realize that I was just kidding myself.
There are things that can help you survive it, like full complete breaths and reducing your effort on the bottom to the bare minimum- scooters are great for this. However there are some real dangers, as Eric mentioned, that can bit you in the butt if your not careful.
First, if you've been scuba diving for some time you've become a C02 retainer- happens to all divers as they learn to breath off of scuba. This in itself puts you at a great risk for deep water black out- also called C02 blackout. This is why full breaths, and no form of "skip breathing" are very important on deeper air dives.
Second, equipment restrictions which will impede your being able to take a full breath and properly rid yourself of the excess C02- this is where aback plate and wing make a much better choice than and kind of a jacket BC, because they can be adjusted out of the way of your stomach so that you can do a better breathing cycle.
Third, by having a long breath hold your not working on your C02 tolerance as much as your hypoxic training- you need to exercise while holding your breath or do some "C02" tables to train for that effect.
So after all of that will freediving help your scuba? Yes. You will be a much better scuba diver if you freedive- just don't count on it to rid you of narcosis. You will use less energy, learn to breath better- especially if you practice any kind of yoga- and be much more comfortable underwater than your non-freediving buddy's. You'll also learn to streamline yourself better in the water and have the confidence to pull off an OOA ascent if you ever need to that just scuba diving alone will not help you with.
One thing that might really help your comfort level in an emergency while diving is to practice, on the couch, so exhale statics. Once you realize that you can hold your breath for a couple of minutes with NO air in your lungs you'll be much more comfortable if you do ever have a situation underwater where you need to share air.
Jon