Is an automatic transmission dust cover needed?

Are you sure that you've got the right dust cover for a 904? I've got a few laying around here and they don't have that small opening on the bottom. The one for my 727 does. They don't interchange. The top 2 pics are of a 904 cover. It's hard to see but the bottom pic does have that small cover on the bottom of the shield and it is on my 727.

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From what I have seen slants don't have the small plate.
My 73 318/904 does. (not sure why some do and some don't besides the drain service)

The small cover hole can be welded up if that makes it more convienient.

From the picture it looks like he has the passenger side brace, and I got that one back on without too much trouble.