Cat 777 questions on build

[Cooper]

Hey guys I have been wanting to build an adt but I think I would benifit more from an off highway dumper. I'm thinking about building something around a 777. Not the big boy 797 and not a smaller one. Some questions I have are looking for the tire size. 1:14 scale build. Where to purchase something for that scale and style. And the other big question I have is drivetrain. I was thinking about using two gear head motors for an axle/drive system. I don't know if any regular axles would be beefy enough to handle the weight and power needed. That was why I was thinking of gear head motors, one for each side built into axle like fumotec uses for the adt. And I have no idea what rpm range would be best suited. 12 volt system I assume I would be using, 100-150 range? Any suggestions would be appreciated. And I have noticed these trucks use two stage cylinders or dump hoist. That may be a challenge. I know the sand master dump uses a screwdriver, but I would really like to keep with cylinders. If any of you have had any of the multi stage hydraulic cylinders apart and a pic of ends of cylinders that would be appreciated too!!! This is in the concept stage and I've kind of decided a off highway haul truck would be easier to make and better suited for the construction company. I think the top of body is around 12" high, that would still allow me to have the excavator load it. Thanks for any suggestions and or input!!!