It's real hard to tell from those photos if that is a crack or just another badly blended area caused by the sand cores not being properly pasted at the foundry. The exhaust ports and intake - boost port ribs suffer from this problem. They look like they're broken when new. The sharp lines create a stress riser that helps bad dreams come true, a real crack.
The transfer rib is an area of low stress and relatively thick material.
Take a small diameter round file and remove some material from the area you believe to be cracked. The flaw may be only skin deep.
Larry
