I put the following parts on my X1
XB wheels (rear needs custom spacers), brakes, forks, triple tree, XBS front headlights/flyscreen, oil cooler, rocker boxes with pcv valves
as far as direct bolt-ons go for an XB to X1... off the top of my head....
handle bars
blinkers
grips
controls
levers
front master cylinder
rocker boxes
pistons
jugs