I've found these sites useful in other builds. Used 2 of the winches from rc4wd.com on my '42 Kenworth wrecker for all the boom operations, and rctank.de has detaill items such as tools and welding tanks. Carson has some more aggressive tires than the stock tamiya, not exactly military but better
than street tires. If your planning on doing any real pulling with some weight on the trailer you may want to look into a gear reduction as well.
As you know the tamiya truck are geared pretty high to simulate onroad speeds and they don't have much low end power even in low gear.

http://store.rc4wd.com/RC4WD-110-War...ch_p_3734.html
http://www.gardentrucking.com/sublis...%20and%20Cargo
http://www.rctank.de/TANK-TOOLS
http://www.carson-modelsport.com/en/...rtNr=500907011
http://www.gardentrucking.com/detail...d#.U6htZvldXng