Well I have always heard welding cast iron is tricky.
Let me add this, many moons ago I had a welded stroker crank, crank was a cast Buick 455,
made a 535 inch street motor with the T/A Stage 2 heads. Horsepower level, who knows, 650 ??

I still think it would be OK to relocate the mount positions on the side of a Mopar block, from a stress standpoint,
but perhaps not from a welding standpoint.