The M26SS engine runs well with the HPI polished pipe. It's what I ran for awhile. You can find them pretty reasonable on ebay (~$25 shipped).
If you upgrade your engine, get an LST or LST2 2 speed assembly. The AS two speed can't handle much abuse.
RPM arms would be a good idea. As would the LST2 two speed rear cover. Keeps the rocks out of the gears better. The LST2 tank fits it and adds more fuel capacity. If your into decent air (jumps), get LST1 or 2 shocks. My stock AS shocks leaked out of the box. I've only upgraded the rear shocks, but I have two more for the front.
The traxxas rims are pretty tough. They are among my favorites. I've never stripped a hex. HPI rims suck. Those are the only rims I've stripped a hex in. I recently got a set of zombie maxx tires on HPI rims... one of the hex's blew on me. I run after market aluminum hex's as well. The zombie maxx tires are awesome tires for that truck (or any truck). They work well on loose dirt, hard pack, grass and some concrete. Too much pavement running will wear them down pretty quick though as they are pretty soft.
Also, the stock brakes start grabbing when coasting after a short while. Mine were fine for a bit, but then they started grabbing for no reason. I replaced them with a vertigo CF disk last week. I ran it this weekend and it was 100% better. No more chatter or locking up for no reason.
Sorry... rambling.
Here's mine how it sits now (except for the wheels/tires):
