CANBUS Tachometer, A Little Help?

hey guys! while this is my first post have to say this site and you all have been nothing but informative, it’s much appreciated despite how much i lurk lmao.

anyway! a few months back i swapped a GM LS6 into my 997 911, i’m running dual ecus (e40 to run GM engine and motronic to run porsche instrument cluster) and while all has been working as intended i cannot hey the tachometer to work for the life of me …

there’s an analog engine signal input at the porsche ecu which ultimately spits the tach signal out via CAN however using a dakota digital sgi8 (sensor input - GM tach signal, sensor output - porsche ecu tach input before ecu, power - 12v switched, ground - to chassis) cannot get such to read so am looking into having an analog signal (e40 tach signal) drive the tach (which is CAN) …

can anyone shed some light on how to accomplish?