i2C : pull-up resistors "design pattern", Shielded cable and connector?
wire capacitance is what you are fighting - you can only go as fast as you pullup resistors can charge the parasitic capacitance of the wires  - in the real world you make a good guess and then once you start working with the circuits drop a 'scope on on the data line - if you see a bunch of nice square waves you're good to go. On the other hand if you see a bunch of shark fins some of which don't make it all the way high before the clock edge you're either going too fast or need a smaller pullup