Lock up converter question

vehicle: 1986 Dodge short passenger Van- carburetor 318/904 8-1/4 rear.
All stock. Factory ignition is that lean burn looking, Over priced, prone to failure ignition computer.

Build up: I’m calling it a A904 but it is actually called a a998 I believe. It appears to be lock up converter and has a single black plug on the rear of the driver’s side pan lip facing forward.
I don’t have a PK# yet. It is very oily and dirty and needs a power wash.

I know little about this converter if it actually is a lock up. I’ve driven this van only a few times around the block due to lack of registration.
Question: from what I’ve read- it is a hydraulically controlled lock up. BUT if you apply 12vdc to the solenoid, it opens the solenoid and dumps the pressure to the converter clutch. Main reason would be for towing or heavy load. Is this correct?
Is this how the 80’s style lock ups work?

My goal is to swap out the computer with a 4/5 pin ecu like we all know and love (and distributor) but because that computer controls the converter - I need a way to shut down the lock up when hauling or towing. It seems simple enough, right?
Thanks for the help-
Syleng1