Gen V LT/8l90 tap shift question

[Lonniec]

I am in the middle of a LT swap on my 67 Nova and am trying to figure out to make the tap shift work…
What I am trying to achieve is to be able to utilize the stock shifter from a 18 Camaro that has the manual slap shift function and the indicator display right beside it. I am running into a couple issues though, a) I can’t seem to find the correct harness to plug into the shifter and the indicator and B) trying to figure out how to tie the system all together!

From what I understand the shifter harness (that I can’t find a pt# for) runs to the bcm with a gmlan wire the the bcm send a second gmlan wire to the tcm to signal the tap up or tap down function.

So my question is this, can someone with experience tell me if what I said earlier is correct and what other headaches will I run into by wiring a bcm into the car? Will the bcm also need a communication with the ecm? Will the bcm work right if all of the other circuits dead? And last but not least how hard will it be to flash a bcm to communicate with all my other systems?


i hope this belongs in this forum…. I feel it’s definitely on the more technical side lol