Might rain, so I got the cardboard out, slid under with a handful of sockets, and here are the E450 sizes, through Chassis Year 2007:
Front and Rear Sway Bar Center Bushing Brackets: Metric 15MM
All parts furnished by Hellwig: SAE 3/4"
There isn't an SAE size that'll "work as 15MM" so you need that specific socket. Standard depth is fine.
You can get away with 19MM for the 3/4" but the socket should be Deep.
I always get Six Point Sockets.
So you'd need a Ratchet, two Sockets, and a Wrench.
Wrench can be an Open End, Combination (box/socket end plus an open end) or an Adjustable. 8" would be nice, but a 6" will open to 3/4".
Again, suggest 1/2" drive for the sockets. I don't like the fastener diameter much bigger than the square drive size of the socket set. The 3/4" tools will be working 1/2" fasteners, and the 15MM is driving screws that are about 7/16".
Footnote: 2008 and newer use two different sizes on the front bar center brackets, the 15MM and something larger. Common next larger'd be 17MM but I don't have a vehicle to check that on.
EDIT: Looked at the OEM rear sway bar end links I removed to install the Hellwig bar. The 3/4" or 19MM socket will remove the frame end. The bar end is 14MM but your 15MM socket'll catch it if you get a six point. Or if your open end wrench is an adjustable.