Some info that I know
The hole in the front of the block has a breather tube and oil cap on in industrial applications . I was driving across the desert in cali and saw one on an irrigation pump. And the camera was out of film
I have layed the gas IH block next to our IDI and the only similarities I could find were that they are both damn heavy.
I put a 460 up to my diesel zf and only the top 2 holes lined up and they are not exact, I drilled and reamed the bell to accept the dowels and bolts for the 460.There was enough meat to do it, Looks like they use the same casting for the gas and diesel Zf.
23 years with a wrench in my hand making a good living so I know a little about a hell of a lot. :Sly
Love thes site
Russ