I broke that same part. I just purchased a new one from the dealer but you could search around the wrecking yards for a used one too. When you buy injector seal kits, that nipple part that is broken comes with it. You need to boil the nipple for a good ten minutes or so to soften it enough to sqeeze on the end. May want to buy a couple extra just incase you break one. Is also a good idea to have your injector professionally cleaned, and balanced, they will replace all the parts for you. Also a good time to take off your starter and replace the brushes and what not, alot easier to get to right now.

Good job! Post a pic of the valve side of the heads if you get a chance. Are 5 & 6 burnt?