What is this? Green box under dash wiring???

Ok... didn’t read far enough!
Wow, so I’ll try bypassing it first but may try using the 73 wiring harness and completely do away with the 74 harness.
My only problem is the 73 harness I have has been butchered on in places. I’ll try and combine the two then look elsewhere for a virgin harness.
Thanks again for all the great info, I want the interlock system gone!!!