I think he might be talking about the small 250 6 from the Falcon engine series.. which are bullit proof because of the 7 mains and the good oiling system... however a 250 crank will not fit a 300 as they are 2 completly diffrent engines...
There is a new aluminum high performance cylinder head that will be released at some point for the 240/300.. produced by
www.classicinlines.com