I have one very rare hard to find "Big F" 427 MR C5AE-6090-F head.
This is a very first version of the medium riser head. Called the "big F" head. Probably one of the best street fe head Ford ever made. Numbers vary but they were a 30-50 HP better performer head than the regular production medium riser head. This comes with a 427 MR rocker arm assembly $1,150 shipped and insured to you if in the US. Message me with e-mail address for more photos