Hello, i have a 1999 mustang gt. im trying to figure out if my engine block is a 5.4l or 4.6l. i think one of the previous owners might have swapped the engine because the heads on the engine have the code RF-XL3E-6090-C20D PI. that code correlates to a 1999 f150 5.4l. and i am trying to figure out if my block is a 4.6l or is the entire engine a 5.4l. anyone that knows how to figure this out please help.