I was going to post my tower wish list which from my end has all of the parts listed that you need. However once I tried it and then clicked on the link I couldn't see all of the list and what was viewable didn't have all the parts shown that you needed so I just edited this post. Anyway I'll give you a list:
86030 43t ring gear
86031 13t pinion gear (make sure it's all black and tower has been selling the new black ones)
86032 bevel gear set (you need 2 per diff cup)
b032 10x16x5mm bearing (you need 2 per diff cup)
b085 8x16x5mm bearing (you need 2 per diff cup)
85044 diff cup (2 per pack w/gaskets and plastic brake hub)
bs107 kyosho bevel shafts (6 per pack)

And if you really want to make this mod extra strong then you can do what I did and use:
http://www2.towerhobbies.com/cgi-bin...9&I=LXHCA3&P=K
http://www2.towerhobbies.com/cgi-bin...9&I=LXESX2&P=K

I would highly recommend that you use new bearings when you do this and keep extra b032's on hand as they tend to wear out faster than the larger bearings.