There are a number of things that you should look at strengthening for jumping purposes. All were mentioned in one form or another:
1. Beef up the suspension. Jumping a heavy RC requires some beefy suspension to save the truck from bottoming out and destroying itself. Better than stock shocks. I recommend some aluminum bodied shocks with heavy weight springs. RPM towers offer some forgiveness in the way of flexibility, but a strong suspension need to have a solid foundation. I'd recommend some aluminum towers and some aluminum bulkheads. There are quite a few out there to choose from. As for which shocks, the big bores, 1/8 scale buggy shocks or some UE shocks (which are basically the same as a set of 1/8 scale buggy shocks) are all good choices.
2. Skid plates are a must. Under-armor for the truck will protect the tranny, the steering servo (if you use a servo skid plate) and the differentials. If you can afford titanium or spring steel skids, those would be the best. Aluminum skids are a waste of money in the front and rear skid position. Having to bend and reshape them after every bash gets to be a real pain in the ass. My recommendation for the cost effective solution would be to buy a nice center skid from any material, a decent steering servo skid, and stick with the stock plastic skids (they are cheap to replace if they get busted up). If cost is not problem, then spring for the titanium skids or the spring steel skids.
3. Upgrade the steering servo and the steering set-up. A hi torque steering servo is a must for bashing this off road truck. The integrated servo saver steering horn set up is probably the best also.
4. Upgrade the stock engine and pipe to something more to your liking or tune the stocker for perrformance...it has been done before.
5. Anything after this list is purely up to you, but there are a number of mods and upgrades available to make the T-Maxx a stronger ride.