I sure can't see a small block Chevy lasting long on gas/oil mix...
I did not say you could do that! I said you could design an engine as large as you wanted with gas/oil mix. Of course an engine with soft babbit journals will not hold up to a fuel oil mix. They will be ruined in a matter of minutes. An engine that size would need ball bearings made for this purpose. Engines as large or larger than a small block Chevy has been made with mixed fuel oil before.