The plastic spacers allow for a wide range of adjustment in the wheelbase, roll center, anti-squat, etc. etc. etc. Lots of little tweaks you can make after you're "done" building one of these.
You don't have swaybars installed and the spur-gear cover isn't fitting properly. The swaybars are an essential upgrade for this chassis; all four of mine have swaybars installed in various configurations. My FWD XV-01, probably the best dirt-slider of the lot, has the thinnest swaybar installed in the front and the thickest swaybar installed in the rear -- the opposite of the other two that still have the motor mounted up front, but as it happens the thickest swaybar in the rear makes it slide marvelously. Tune the diffs to provide traction, and tune the swaybars to control chassis roll and to make the axles unload when you want them to.
Don't worry about the tie-rod ends hanging up on the chassis, you can bevel the lower edges of the tie-rod ends to make that less of a problem if you want, but it generally doesn't have any effect on the vehicle when it's supporting its own weight anyway.
Here are my two rally builds, for reference:
4WD:
http://www.rctech.net/forum/electric...a-xv-01-a.html
FWD:
http://www.rctech.net/forum/electric...-xv-01-ff.html
And my two on-road builds:
Rear-motor 4WD:
http://www.rctech.net/forum/electric...a-rr-01-a.html
Front-motor part-time 4WD:
http://www.rctech.net/forum/electric...01-sh-awd.html