If I take both door mirrors from a 2003 hd (Folding type) to a 2005 hd, (non folding type) Do I need to also transfer the door panel switch, then also do I have to reprogram the bcm, Thanks in advance.
You reprogram the DDM (Driver's Door Module) to enable the folding feature. You'd only need to reprogram the BCM to enable things like curb view assist.