If the mobo is in a case that will probably not work to well, unless the side cover is removed.
Also why barbs??? Why not just hack the copper pipe off about 1.5" up from the top of the block and use the copper pipe as the barb? Couple hose clamps should work just fine to seal it up.
Also what did you use for the base? Looks like round copper pipe, but what is the base, or how is it installed on the pipe, or...???. In other words show a bottom pic!