M103 head bolt tool?
 

Can anyone tell me the size of the tool needed to remove these?

They're the triple square from my memory.

It costs about $25 at the dealer and is well worth . Any after market tools will destroy the bolt when you will torque them.
P/N 617 589 00 10 00

12M . . . I've used an "aftermarket" driver for years without harm.

I too subscribe for the MB tool or FACOM.

Why would you reuse the same head bolts? Aren't they one use items?

No. They are only replaced if stretched beyond spec.

Hitman, yeah, they are the 12mm,12-point torx type.
Do not even try to use a 6-point torx!!!!
Pep boys sells a set that has the correct size.
But, as stated above, those head bolts are on REALLY tight if they are original. So, the cheapie Chinese tool might fail.
Here's a tip; when you are loosening them, take a strong pull on the wrench, then have a buddy tap the top of the breakover bar with a large hammer.
They are screwed into the iron block, so you won't hurt anything, and the tap helps break them loose. Kinda like a Vessel hammer-impact driver we used on motorcycle case bolts.
When re-installing the bolts, be sure to check and oil the washers under the bolts (new bolts have washers built-in). If not, they will gall when you pull them down (personal experience).

DG

Picked it up for $19, gotta love half price days. :D