If you do a search about front brake calipers there is a lot of incorrect information passed on over the years. I was going to add to one of the existing threads but it will get lost and anyway its a bit pointless at the end of a long thread so this will be the first post.
Since the beginning of time it has been reported that the original Nissin front brake calipers fitted to all years of XR1200 are the same as the ones fitted to various Honda motorcycles typically RC51 SP1/2 and various model Fireblades.
Over the years I realised this is not the case, the caliper fitted to the XR might have similar architecture to the Honda variant but its design, appearance and particularly the position of the mounting lugs is quite different. I have not seen the XR casting used on any other manufacturers motorcycle so can only assume it was specific to Harley-Davidson.
This is your Nissin XR1200 front caliper
This is a typical Nissin caliper fitted to many Honda motorcycles including the RC51 SP1 and SP2 , Fireblades and various other CBR models.
The brake pads fitted to the Honda destined calipers will however fit the XR1200 giving much more choice of manufacturer, material and cost. This is probably where the confusion started!