400 with TF 240 heads - valley plate options?

The nice valley plates only work with the raised port heads.
As far as standard style heads, (I have RPMs) In the past I had problems with the stock pan/gasket sammich keeping a good seal underneath so I've used the 440 source sheet metal and the 2-piece Hughes units. They all sucked....they just don't seal well. There are big gaps at each end of the bent-down edge that fits under the head, and yeah you can fill it with 'right stuff' or your favorite sealant and it will still end up leaking.
And I used to think it was stupid....but what's actually worked really good is trimming the port flanges off the stock tin pan, and bending the edges down so they fit under the heads. Some ultra gray and no problems. It's kind of the same idea as the 440 source pan, but it's very easy to trim to fit nice and tight, looks stock and fits under any intake. And.....cheap!