There isnt too much you need to upgrade then really- common weak points are:
Bulks
Towers
A-arms
Diffs
Chassis
For bulks, you could go the FLM or GH route for regular aluminium items.
For towers, I'd Go FLM or UE knuckleheads.
For A-arms, RPM items are probably best ( maybe true-track rears )
For diffs, you hav3 3 options:
1.
http://www.rc-monster.com/forum/show...t=9153&page=15 LST2 diff mod
2.
http://www.rc-monster.com/forum/showthread.php?t=8012 /
http://www.unlimitedengineering.com/...ore/13540.html UE Ultralites
3.
http://www.beatyourtruck.com/forum/s...Best-1-8-diffs FLM Hybrids ( in which case you wont need regular bulks )
For the Chassis, there are a couple options still:
1.
http://www.rc-monster.com/proddetail...lm10900&cat=31 FLM 3905 chassis
2.
http://www.amainhobbies.com/index.ph...filter_mfr/144 Xtreme Racing CF 3905 chassis
If you prefer aluminium + low CoG, then consider doing a little work like this:
https://picasaweb.google.com/buikpij...rbonLowerplate
Overall though it isnt a huge amount of work or money that needs to be expended on the truck to make it something really special..