SOoooo you had the heads off but didn't pull any pistons , especially those two?????

The Ford FE engine firing order fires 7 and 8 consecutively? and if the ywo plug wires are routed next to each other can cross fire the other cylinder---the factory wire routing of the spark plug wires on the left bank from the factory across the valve cover 7, 5, 6, 8------if you put the wires on the plugs without paying attention to things, you will have #7 wire on #5 plug, #5 wire on #6, #6 on #7 and only #8 correct---------this will cause problems with the way it runs----------------