Lockup vs Overdrive

Hello all. I have used a 200r4 trans for the first time and bought it used. I have it installed in my 57 Chevy Wagon due to the size is a perfect swap for the 2 speed power slide. I rebuilt the trans with a manual and had no issues. The converter that came with it was unknown if good or not. I just started the car for the first time after the build and before the start I put a gal of fluid in. Started for a min or less and it had a loud knock. Checked fluid again and did not register so another gal of fluid. I did this so I did not over fill. started again and while in neutral to check the fluid the knock almost went away but still now and then I would hear it. The trans took 1.5 more quarts of fluid. Level checks good but still get the knock mainly when the engine first starts and then goes away for the most part just a knock every now and then. I put it in drive and it drives the rear then back to neutral and the rotation slowed down almost to a stop so I feel good about the build of the trans and I know there are no issues with the engine so I think the knock is coming from the converter. I have no idea what type of converter it is (lockup or non-lockup) or the stall. I figured I would get a new converter and take a shot in the dark but I know nothing about converters. If I go with a converter and it does not say lockup in the description that would make it a non-lockup? Do I have to have a lockup converter for overdrive to work? This is not a race car just a cruiser and show car. It is still on jack stands so taking it out for a spin is not an option at this time. What would all suggest for the converter lockup or non and I would think a low stall like 1600-2200 from what I have read. This should help keep it cooler and because its not a race car. I understand I would need to wire the lockup on the trans.
Thanks ahead of time for your opinions and help

David Husek

Turbo Buick Performance
Lots of questions and I can help you with all of them. I would suggest giving me a call to discuss. The knock was from starting the trans dry. David 516-285-1103