dropped the ecu out of my 1994 ef fairmont auto sedan today to swap it and I noticed 2 strange thing

1. the code is 4dcd- is this not for a ef fairmont wagon? if so can I use a 4dcc or 4dcg ( both have same diff ratio from the tech doc)
2. the second wire down on the rear end of the car side ( salmon looking colour with white stripe) has been cut and a new wire attached ecu side that I trace to the engine bay and then it goes missing....... whats this wire for?
Really trying to start this car so a response would be great please

they also have a 4dce i might be able to get and from what I can read is a police option, will this go or will it cause problems?

I have traced the wire, it runs to an orange wire that someone has put in and connects to a black wire that seems to go into the loom down near the auto, so I dont think thats going to stop it starting.... there is no switch in the wire. Back to square one. I take it either a 4dcg will go from what I have read on here but what about a 4dce?

The last character of the catchcode is normally the revision. As they come up with new tweaks or fixes, they increment it by one, so a 4dcg "should" be more sorted than a 4dcd, and 4dcd better than 4dcc - but I haven't heard of anyone who knows what the differences are between any two revisions, so they can't be that major. AFAIK, any 4dc* should be able to be swapped with any other 4dc* without noticeable issues. Personally, I would go for the latest revision as it should theoretically be better than earlier ones.