This has been so confusing so a e-mail to Gene.Vorwerk@kuryakyn.com and a follow up call to Gene at Kuryakyn has finally cleared the issue up for me.
There are only two throttle boss that will fit the #6383 black ISO Grips for the F6B heated grips. There is the #6314 which is black and is the longer one like 53driver has and the other is chrome #6242 and is the short one that I want, but Kuryakyn does not have the short #6242 in black (I'll paint the one I just ordered).