[urq] Removing URQ headbolts for the first time?

[quattrodude at comcast.net]

I'm replacing my head gasket on my 83 URQ and need to remove the headbolts, however, my first thought was they would come of "somewhat easy with a short ext bar"...NOT!
I have the correct triple box 12mm adapter, but since I dont want to shear off the bolt applying sideways force with an extension bar, does anyone have an secrets? I thought about using an impact wrench? anyone have an thoughts on that too? In the same manner I dont want to strip it out either? The triple box socket fits pretty snug but as many of you know, things happen fast with an impact wrench (thats assuming even the impact wrench has enough torq).
Or are these bolts really that strong? that i dont need to worry?
Thanks all in advance!

JP Chaplen