I have had little to no contact with ZZP other than many years ago when I was looking at massaging the LN3 in my Reatta. Their response was "why?". At the time I thought that rather rude but since that time I understand that the Series 2 is a better platform to hot rod, so, I get it. My tuning help has been Ryan at GM Tuners aka Sinister Performance. I found that all input is helpful. Much of the adjusting for deleting missing components, like the transmission gear indicators, just involves turning off the various items in the chip. The operating system to make the engine run have remained pretty similar all the way up until the 3800 was discontinued, so making it run with the Reatta dash intact is pretty straightforward. A guy called Betsy Blue (I think) did a five speed on the LN3 or L27 many moons ago.
I have run out of the energy, as well as the time, to do any major modifications, plus I am too lazy to work a third pedal, but I say, go for it. I still may add my half turbo to my Series 1 supercharger, since I have pretty much all the parts, but ...🙃
I should say, his car was Betsy Blue and I think his name was Greg?