I ended up using Autolite XP Iridium in mine after trying a set of Bosch, and the XPs have been good to me...
The orginal Motorcraft were not available, the right and left banks have different part numbers on the 3.0 FFV V6, so I went with the fine wire XPs.
There has been some posts on theRangerStation forms by Bob Ayers about trying to find the OEM plugs, and he like to stick with stock.
Can't find that post or link right now, but will check later....
When changing plugs I found that there are very few threads to hold plug into head, so you have to be careful not to jam or cross. I also ended up replaced plug wires as two of mine OEMs broke off at the plug when removing.
Good Luck !!