I wanted to buy just the intake from Bogner, but he wanted to sell it with the heads. I didn't have the cash for both at the time.

I think I'd start with the 518-M heads if you don't already have the heads. I don't have any of the revised port heads, but it looked like they improved the transition from the seat to the exhaust port on the standard 518-M heads that I bought on a clearance sale a couple of years ago.

Here is a picture of the P5007494 chamber. It pretty much looks like the standard 518-M if I remember correctly.