If you're looking for help and want to draw people in who can assist you, use a descriptive subject title when posting your message. In other words, "2008 LaCrosse" isn't going to indicate to anybody that you need help. However, "Need help with my 2008 LaCrosse" will. Be as descriptive as you can. Please use common sense...
2002 Park ave, 1996 RMSL, 1995 RMSL, 1995 RMS, 1992 Lesabre (My first, That some BMW totaled)
I could be wrong but if you're swapping from a 1996, then it will have a crank sensor to comply with OBDII emissions. 1995 (my model) and down used OBDI emissions, and instead of having the crank sensor on the timing cover by the crankshaft, they basically used the information sent by the optispark to provide the same effect as a crank sensor. So if you're reusing the same PCM and harness from your 1994 you may find that you shouldn't have to plug this in for it to run, although if you're swapping PCM's you will either need the harness from the 96 or run a wire. (Not even sure if you can swap PCM.) Again, I've swapped and played with old school 350's but I don't know half as much as some people on here, these computer controlled car can be tricky so someone correct me if any of this was wrong.
I also think, if you leave the CKPS disconnected, the engine/PCM would not know what was the year the engine that was installed. It's the same engine, with different PCM's and sensors. Why will it not start? Do you have have fuel pressure, spark, or is the starter not turning over. A Lot of questions need to be answered,