Ford has been using cast SADI (selectively austempered ductile iron) cam cores since the 1980s on roller applications with no problems. Millions of 5.0L engines in Mustangs, Explorers, etc went hundreds of thousands of miles with SADI cams. GM used these in a lot of OE applications too.
As long as over the nose spring load isn't excessive, and the profile isn't too aggressive, there shouldn't be any issues. Running a cast core eliminates the need for bronze tipped FP pushrods and bronze distributor gears. Been running a SADi core Howards roller in my '69 350 engine for ~5000 miles and 3 seasons. No issues, and I sleep well at night.
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