I honestly thought that someone revived an old thread when I first started reading this post (the posted article is 5 years old now)
A few points after reading through all the responses
The P5 head has been around since the 90's were designed by Mopar to replace the W8 head in Pro Stock Truck
The P5 heads were first used in the early 2000's by Australian Pro Stock Racer Jon Andriopoulous with an Eaton Enterprises built engine, and later built by RWR (Rick Watters Racing), or it might have been PRE, I can't remember exactly.
Lee Bektash won the 2015 title, and ran as quick as 6.87, while also breaking the 200mph. Those performances have not been touched since. He started with PRE power with cast heads, billet headed engines came from RWR (Visner heads) and finishing with Slawko topped BRE engine.
The first billet P5 heads were done by Visner Engine Development, Slawko makes the heads that BRE uses now. Both heads were developed for Australian Pro Stock. The billet head came about because the cast P5's were sprinklers when maxed out. They'd often crack in the valve bowls etc, as they were originally designed for 358 cubes. I think the intake valve size is getting up around 2.36" these days, I've only seen the earlier stuff, so I'm not 100% sure.
Blocks are an issue for these engines, the early R4's were best, but most require sleeves in all 8 cylinders and the block to be filled.
When stop using off the shelf parts, they all cost lots of money, regardless of what's on the valve cover.
