The gen 1 Sport Trac was not available with a V8 and the Explorers that did have modular V8s from 2002 to 2004 used two-valve cylinder heads. Not sure how easy it would be to swap three-valve heads onto one of those blocks but I assume it can be done. Explorers prior to 2006 also had a different frame design from the gen 2 Sport Trac so they might also have different engine frame mounts although I assume the blocks would have the same engine mount bolt pattern but maybe not...
If the Explorer and Mustang both used aluminum blocks during that time period why not just use a Mustang block? Also, why not use a Mustang block from 2004 thru 2010 which would already be set up for three-valve heads? Three-valve heads also require a higher pressure oil pump to run the camshaft VVT. Will a three-valve oil pump bolt onto a two-valve block?
