I have a 250ci crossflow out of an XC. The cast iron head is showing signs of age in as much as it needs valve seat inserts, valves and guides, and a skim, so the hunt for a replacement has started, Seems all the serviceable cast heads are extinct and although I would like to stay with the cast head I have been offered an alloy head off an XE/XF. My question is "Will the alloy head fit the older engine without modification?"