i see people running the mmp and the 1415 combo, the description says up to a 6.5 lb truck , would i be happy with this combo and if so could someone give me a part # for a pinion that will fit the 3.2mm shaft, the shaft does seem a little small compared to the tekin shaft wich is 5mm , will this combo live in this truck with everything else in the truck due to its weight?????