Triggering Camera - this is explained in the Instructables, and works by splitting the external trigger cable.
3D parts - You can download the parts (but they're quite big since they're meant for 8-16-35) here, and print them with someone locally or send them to be printed online at a place like Shapeways. An alternative would be to get the 3D files from this project (look in the 'hardware' folder), which is designed specifically for 8mm.
Resolution - totally up to you. Rule of thumb is usually to capture at the highest resolution possible and then downgrade the quality as needed for whatever platform you're publishing to.
Histograms - I do not have knowledge in this area. Hopefully someone else will chime in.
Camera Choice - the DSLR choice was made for the first Kinograph because I wanted to use components that everyone could get their hands on. This works, but the DSLR is not a good choice overall because of the mechanical shutter, which breaks after extended use. For the next version, I am exploring other options including machine vision cameras, cinema cameras with global shutters, and Magic Lantern + Linux hacks on Canon DSLRs.
If you know anyone with programming experience with Magic Lantern, please let me know!