R4/P5 hard to find the original parts as these are from the NHRA Pro Stock Truck days.
This engine could be run in NHRA Comp Eliminator or NHRA Super Stock in Modified, or with a single 850 or 750 carb Modified Stock.
Most of them seem to be 358 CI.
You can build one new with a Ritter block and Slawco heads.
Patterson-Elite maintains them for a Comp racer and an Super Stock racer as I have seen the engines (in crates) there.
Edit, just realized this is two engines, one with the drag race (Hemi heads) and one with what I call the NASCAR heads. Not sure if those were drag raced on the trucks or not. Maybe someone else knows the history better.
Whilst the Ritter block could probably be ordered with a blank deck and lifter valley, they are too tall a deck height for anyone to run them in Super Stock or Aussie Pro Stock, perhaps as a larger engine sure.
The early Wedge P5 heads were the first iteration of of the P5 head and never made it to Nascar. Tim Davis used them a bit years ago where "wedge" heads were allowed. The bowls on the cast heads were prone to cracking, hence why the billet ones are so popular.
As always, blocks are the issue. The R4 weren't consisitent, many of them have 8 sleeves and a decent grout fill.
