Is it possible gm actually used the diesel blocks in a 77 cutlass supreme as a gas application?Curious about this because i had a 77 cutlass supreme in the late 80's i bought from the original owner .It had a low end knock so we decided to rebuild it and thats when i found out it was a diesel block .Back then i payed no attention to block stampings ,otherwise i could had simply identified it from its stamping.The knock turned out to be a rod cap hitting the oil pump pickup. It was indeed a stout motor when we finished it and if i knew then what i know now yada.

 

No. There's no way the factory would have dealt with all the differences under the timing cover, not to mention the injector pump boss just hanging open. Especially considering they had the windowed 350 gas blocks which made much more sense at the time.
The diesel->gas conversion has been known for a very long time, so I wouldn't be surprised if that was one of the earlier conversions.
Did it actually have a large "D" or "DX" on the side of the block?

 

I honestly dont remember what numbers were on it and at that time was only concerned with getting it rebuilt .My brother in law did the work at the garage he worked at.The original owner wasn't very mechanically inclined so i doubt he went out looking for a diesel block for a replacement ,but who knows how it got in there.thanks for the response