The Jaco foams are for the rear of Associated trucks there the same od as the stock tires but about a 1/2" wider I got them from tower.
http://www2.towerhobbies.com/cgi-bin...&I=LXCME3&P=ML
Any 2.2 tire will fit if you want bigger try the 2.2 truck tires?
Here's the servo it comes with an aluminum arm.:)
http://www2.towerhobbies.com/cgi-bin...&I=LXCRT0&P=ML
I just noticed on the BCE chassis he is using a Futaba s9550 low profile servo that looks very interesting check out the specs speed .11 on 6v and 83 oz-in torque a little pricy but looks like it would be worth it?
http://www2.towerhobbies.com/cgi-bin...&I=LXXJ36&P=ML