Hello The1. I think I came across some posts written by you or some other mate (sorry, can't remember the name. Tazy?) on Just Commodores. I remember someone mentioning a special T1 with Lilbug monitor ROM.
Anyway, GMB Tech1's covered from 1991 to 1998 and I don't know what size a regular cartridge would be. I think all were replaced by MSC's. And even those, are very, VERY hard to find. I just bought mine and I am reluctant to make any attempt of reading it, because I'm afraid of damaging or erasing it.
I have a spare GM/FORD/CHRYSLER PT cartridge that uses a larger AMD Flash (don't remember the size now) that may be useful to write this dump. Probably it is in the 512kB-1MB area. As I said before, the challenge is to fit the data in the right pages, because code runs from the cartridge and any wrong byte could crash the application.
I will take a look at vpecker. Didn't know about it.
GM Brazil from the 90's are most based on Opel designs under the Chevrolet brand (Corsa, Kadett, Vectra/Cavalier, Monza/Ascona, Omega), but with a few differences. I have two Omega-A I've been able to use an Opel cartridge to both, one with the regular option (basically the same car) and another, which was sold only in Brazil, with the Motronic 2.8.1 from the Omega B. Most of then (maybe all) runs on KW71/KW82 protocol instead of the widespread ALDL.
I also own a 2004 Vectra that has its modules updated from the original 1997 Opel Vectra, so an Opel program will just connect to Climate Control, ECU, TCM and Immo. I bougth a VCX Tech2Win clone for it (And still had to make some reverse engineering on it. Basically it cannot switch the various DLC pins used and do not work with the 200-baud init. Only 5-baud and KW2000).
By the way, from 1998 to 2011 we had Holden Comodores (VT, VZ and VE) rebadges as Chevrolet Omega here