Originally Posted by second 70
My guess is it's a P5007671 wedge mega block. Might be a unfinished block I can't tell from pictures if lifter bores are finished. It is a Motor Castings foundry block. It's the only one I found listed with 2 bolt mains. Zippy is the guy that would know more but I haven't seen him post in a while.

Mike
Thank you, much appreciated. PJ