Not sure what valley pan is currently on my 440 but I keep seeing oil at the front corners. I have edelbrock performer RPM heads and intake manifold.

Is the AR engineering 1 piece aluminum plate a good fit for my set-up?

If you didn't use enough sealer on the corners that seeping will happen. I take it you do have a pcv set up on that motor.

You can't use a billet valley cover with a Performer RPM intake manifold unless you mill off the crossover.

Yes I run a PCV. Also I should have been more specific its an RPM airgap intake

I now add a slight bead of RTV to the upper edge of the head gasket during builds. It seals the corners better.
Doug

Replacing a valley plate in the car with the heads on can be tricky to get a leak free installation. I would just replace it with a factory type bathtub gasket properly sealed on the ends. Otherwise you will need to cut the old loose from the heads and try to remove ALL the sealer from the block and heads. If you do decide to install a billet valley plate go for the one with the removable plate so you can access the lifters if you need to. Like Andy said you will need to remover the heat crossover on the bottom of the intake manifold. I had to do that on my 493 with an Indy valley plate and Performer RPM intake. It's a big messy job and hard to apply the sealer evenly unless you remove the heads. I'm not 100% sure you can use a valley plate alone to seal with Eddy heads without some kind of filler plate like the ones Andy sells called "bat-wings"
Gus

I was think of having a bar support like a factory setup but all 4 sides.I was also designing a lifter valley windage tray to prevent oil splash.I guess this gould go in up or down with a finger slot to grab it.

I have an Edelbrock performer RPM so this gasket won't work either?

https://www.manciniracing.com/mara1pivaplk.html

Not unless you cut the heat crossover chamber on the bottom of the intake manifold off. I removed mine with a steady hand and a cut-off wheel so I could weld it back on if needed. You don't need it with most aftermarket heads because they don't have a heat passage. You cant see it anyway when the intake is bolted down

Gus