Ok, I've found I can swap out the 351w heads with 302 heads by boring out the holes for the headbolts. I've picked up a set that had been redone over a year ago. Pump gas here now has 10% ethinohol(?) in it. Do I need to have the valves and valve seats redone or ir stock ok with this fuel? The 351w has a blown headgasket and the 302 heads I got pretty much for free.