One would almost always want a 4 row head on a F series.... Yup an F438. I have seen one 3 row head for an F in my life, but that is just odd for fitting the drive wheels in....
Both heads are mostly galvanized. The older one has orange trim. The newer ones have black trim. The last year or so they had green trim for the Duetz years.
The older heads used one set of drive sprockets on the cross shaft of the combine throat. The black heads used a different size set of sprockets. Likely match black sprockets with a black head, orange sprockets with an orange head. Don't want you to be surprised when you hit the field.... ;)