I looked at the Diesel Giant site and decided to say something. Sorry for the blury picture.
You will need a 1-1/16 or 27mm Deep Socket. However, some of the less expensive Deep Sockets have a reduced area and metal in the upper part of the socket. Sometimes that bends the little Fuel Return Barbs/Nipples.
In the blury pic is the Craftsman Deep socket that have been using on Injectors since around 1975. Looking inside you see it is deep all the way to the end of the socket except for the square hole needed for the 1/2 inch drive.
Buy some Injector Fuel Return Hose before you start the Job as the local part places do not have it. The exception I have been told is NAPA Sells it.
If you buy the Injector Heat Shields locally they will cost $3 or more each.
Where to buy fuel return hose
Diesel Injector return lines, where to buy?
The Thread with the part numbers
fuel return line replacement part
After you install your Injectors you will need to Bleed the Air out of the Fuel Injection Hard Lines. Simply run the Injector end hard line Nuts down till the bottom and then back them off a turn or 2 to leave them loose.
Crank the Engine until fuel is coming out of all of them and then tighten them; and try to start the Engine.
(Besides pumping on the Hand Primer to clear the Air out of the Fuel Injection Pump Housing the above Bleeding Process needs to be done if you have run completely out of Fuel.)