Bearings:
http://www3.towerhobbies.com/cgi-bin...5x11&search=Go
You have to use regular (non-flanged) 5x11x4mm bearings.
The teflon spacers are to take up the slack that you will get due to the different axle lengths between the Rustler and 4-Tec.
If you do this mod I would recommend aluminum carriers for the 4-Tec as the plastic ones you linked are not made to handle the rigors of off-road. I broke my fair share of them before I realized this.
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz