Normally racers want to keep it light, but I'd still suggest the al bulkheads.
These are the best ones I've found:
GA Bulks, Full Kit with braces
They are made of 7075 al which is extra hard and durable. As for skids, I'd recommend RC-Solutions spring steel skids over any aluminum ones out there. With these skids, you don't need a bumper. And they are pretty cheap for how durable they are. THis is RC-Solutions site:
RC-Solutions
I'd stick with stock shock towers. RPM ones are too flexible for racing, although, that's what makes them indestructable, but it hurts your shock movement. Besides, stock towers are cheap and pretty easy to replace. I'd never suggest al shock towers. You need something that either gives and returns to it's original shape (RPM) or something that is a good cheap weak point (stock towers). Running aluminum towers just opens you up for breaking other parts or tweeking your chassis.
If you must go aluminum with the towers, don't buy integy's. They bend like butter. I've read the GPM's and megatechs aren't all that great either. I have heard the hardcore racings are really durable
HCR Shock Tower
ACNCM makes pretty good stuff, but they have the basher in mind. They don't remove any material that others do to save weight. Everything they make is extra beefy.
ACNCM Tower
All I can say, is don't skimp on the bulks. They are one of the most important parts of the maxx. If you have solid bulkheads, it helps protect your maxx from head on collisions and from tearing itself apart when cartwheeling off the track. I never bought the GA bulks, but a friend of mine did and the kit is sweet. Just make sure to get the 7075's.