What kind of transmission dipstick needed with a steel midplate.

Flexible will definitely be easiest.
You are going to run a flex plate shield too.
I have a mid plate and flex plate shield and the notch in the shield is not really big enough.
However I might redo my mid plate since I don't want to pay for that flexibility locking dipstick, it's expensive
I know what you mean I purchased a flexible lockable one and it was 140.00 dollars and come to find out it wasn’t the lockable one they sent me. So I have to send it back! And I’m just looking for a cheaper way to go.