I did not do this, however I did swap a early 406 controlled by thirdgens 7730 ecm into 94 firebird v6 car. So if someone is looking to try a 4th gen dash, there are answers here you will want. I just got a bug in me to try and make things work. It started with just the speedo, the factory vss put out 4000 ppm, which you could wire directly from vss to speedo in that case being it reads 4000 ppm. However my t56 vss has much higher like 10000 or something.
I changed prom inst. pulse divisor to 32 which gave me a reading of about double - further playing got me nowhere with pulse divisor. I found that the ecm cruise control output is 2000 ppm. Hooked it to there and it seems pretty close.
The factory tach up to 97 I think got signal from coil negative - easy one there. The factory temp had a 2 wire sensor, just for giggles I hooked up my thirdgens single wire - and it works great and accurate as far as I can tell against auto meter, and hand held pyro, last was oil pressure, I had already had auto meter temp and oil gauges, but just wanted factory's to work, so I tapped into autometers single wire feed, have not started car since being -7° today. but as soon as I hooked it up gauge zeroed.. I am sure the factory thirdgen sensor would contol this as well.
Figure there is someone out there trying to swap dashes, so i thought maybe this would help being it took me days to find all the answers i needed as well as a pinout of factory dash which I will post if anyone interested.

 

This is where I need help with my swap. Mine is a 91Z with a 383TPI, T56, and dash from a 97Z. I've finally got every gauge working properly EXCEPT the tach. Prior to swap the 91 tach worked fine, since the swap not so much. This is my third cluster and had the same results with all three. By the sound of the engine it seems to be idling fine but by the tach it is idling at 1500-1800. While cruising the tach is everywhere, not stable at all. one guy on here said that the LT1 tach got the signal through the ECM so I figured that was my problem, but maybe you could shed some light on this for me. Thanks

 

I've been doin lots of reading here but im coming up a lil short, I have an 85 camaro and i plan on doin the 4th gen swap from a 2000 ss camaro(i also have the 97 cluster) my setup is as followed, 355 carbed with a 700r4, i cant find any info on what i need to make the swap work, its seems as if everyone is doin the swap with either a tpi setup or t5/t56 trans or both, does anyone have a clue to what I should do, please help