Ok, Ill try.
I am 99.9% sure the Fatboy front fender will bolt right on. You would need to stow the wire for Heritage front marker light.
The Fatboy rear fender got WIDE around M/Year 2007 or "08, that wide fender will NOT work. Unless you change to wide Fatboy struts..?
I looked at the parts catalog and I see lots of shared parts for the Fatboy/ Heritage/ Deluxe and they seem to use the same fender struts. Careful, struts changed a few years ago, I have no idea if the bolt pattern changed, not likely.
The narrow pre '07 or so Fatboy fender should bolt right on your Heritage.
The rear fenders of all 3 changed around 2000? and the hole for the ECU may be different. I would think a 2001-2006 Fatboy fender would bolt right on, again stow the Heritage rear marker light wire, and need a different rear turn signal set up.