wow those exhaust bolts are IN there. . . tips for removal?

[strad]

I already hit them with penetrating oil (pb blaster). It's not an urgent project, but I would like to address the manifold to riser gaskets and also the rust stains on the manifolds (latter is why I would like to remove them). I'm also a little afraid that I'll have to replace them based on the amount of rust pieces that I got and am still getting out the manifold drains. So yeah, manifold bolts should come out.

I have a two-foot breaker bar, but frankly I'm afraid to put any more torque on it than I have for fear of rounding out the allen holes. I'll probably hit them a few more times with penetrating oil just to see what happens, but would like to have as many ideas as possible.

It's an 84 351 PCM, and I'm pretty sure the bolts have never been removed. So they're in there about as tight as you'd expect lol.