Solve the puzzle? Draining converter with Magnum flex plate

So I was having some recent shifting issues with my 904 on 5.9 Magnum combo. Occasional 1-2 flare when getting on it and having to back off throttle to get 3rd. Only about 50 miles like this. Normal driving OK. I dropped the pan and had some wear sludge in it. Pulled the filter and the kickdown band strut bar dropped out. Apparently it was way out of adjustment. Still some meat on the front band so I dropped the valve body and got the strut bar back in place and adjusted. Before you say it.......the transmission is going to come out but just not right now. The issue now is the fluid in the converter. I have a 340 2400 stall converter from Torqueflite Patty (RIP) with a drain plug however I am running a factory Magnum flex plate and the drain plug I believe is blocked. Thought about drilling a hole via the inspection cover but worried about a balance issue and debris. Any thoughts on this besides top off with type F and hope for the best? Pan is currently off.

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