Daisho made these tanks with 12mm x 1.5 threads for petcocks, a strange configuration if you ask me.  As you can see Jim has taken them out.  They are easily removed because they are brazed in.  He is going to put a 3/8" in. All the fittings/hardware I have purchased from BungKing. Lowbrow Customs makes a solid tank, the instigator, designed with the Wassell in mind and has a 3/8" petcock.  It has been more effort to transform this Daisho, and a little more change, but to see it happen is well worth the time and energy, while Jim has taken great care and has conveyed the enjoyment from working on it.