I purchased a Colt 20" HBAR off the EE for my next A2 build and went to installed my front sight today and noticed something odd.

I was using an old front sight off of my 16" carbine and went to line up the pins with the grooves in the barrel and low and behold they don't match up. he
Do I need to use a Colt specific front sight and if so, where do I find one of these bad boys?

Thanks for your help

You need to do more reading around here.  You'll find that it is has been discussed here very often that there is no standard for the pin locations.  You cannot swap front sight bases between barrels unless you happen to get that 1 in a million pair of barrels that just happen to match up.  You also cannot buy a front sight base with with the pin holes in place, they will always come with no holes on the sides.