Combining two can busses

[Badger]

I am running two harnesses in my car. The control pack for the engine and a trimmed OEM harness for the chassis electronics and the ABS.

I would like to feed both systems into my Race Capture in order to e.g. get RPM from the one harness and brake pressure and tire speed from the other harness. I am very certain there will be some ID overlap and am wondering if anyone here has been dealing with such an edge case before.

 

[PaddyPrix]

The only other super bastard idea I have is running long ass cables and splicing it so that tire speed and brake pressure from the other harness Y in, and hoping that the signal is strong enough to pull at the OBD. I've got cat 5-6 cables enough if you need some spare junk 18ga wire. Might be a Brent question.