Head Stug Leakage

[1962300]

Freshly rebuilt late 40's, crab cap flathead.
New head studs, washers and nuts that hold down Edmunds Aluminum Finned Heads.
I have broken in the engine and re-torqued the heads.

There seems to be a bit of coolant escaping from one head bolt on each side.
What is the recommended trick to close up the leak?
Maybe roll a rubber o-ring or two down the stud?

Thanks