Which 318 should I build ?

I totally missed that! Good call. Knew they were out there but the first time I seen it in the wild. My vote is now for the IH block with the 78 heads. I figure the IH plant was probably not as balls to the walls for production figures so they may have been a little sharper in the tooling and a little slower on the line?

I have read the quality is better. Probably one of the reasons why they cast the blocks. Here in town, John Deere cast 2.5 GM "Iron Duke" blocks back in the 70's and 80's with good results.