JimJimJimmmy what do you know about the "R" blocks ? That is what this whole post is about, we all have been trying to identify them.
Any chance they are a stock block that have been cast with a high nickel content?
You are beating the high nickel thing to death. ALL Chrysler blocks had more nickel than the ford or Chevy. If you've ever machined or honed them you can tell the difference with a blind fold on.
The high nickel thing is a GM deal. Today, nickel content is almost meaningless. Compacted Graphite is where it's at.
The OP has a run of the mill 318. Nothing wrong with it. The unfilled pan rail gives it away. I didn't need to see anything but that.
I've personally never seen an R block that didn't have the lifter banks cast for 48 degree lifter bores so that ruled out the R block theory at the first picture.
BTW, the X block wasn't released until 1979. Until then, the T/A block was the over the counter race block. It was superseded by the X block which was superseded by the R block in the mid 1990's IIRC.
