Just thought I'd post how I solved the constant burning out of the exhaust flange gasket on my slant. I am aware of the various new gaskets that seem to have also solved this problem, as well as the importance of truely flat surfaces, cleanliness and proper torque sequence etc. In the last two years I've gone through a few non-fire ring gaskets, which seemed to last last about a couple hundred miles, probably helped along by many blasts down the interstate, then switching to the fire ring type. Those lasted a bit longer, but still ended up burning out. This on a new (at the time of complete rebuild two years ago) oem n.o.s. exhaust manifold and new exhaust and pipe flange. All checked for flatness, cleaned properly, all torqued properly according to the book.
Just was'nt meant to be in my case
I had wanted to have the manifold machined for a doughnut style sealing but never got around to it. Newer tech. gaskets aside, I have been giving it thought about a simple way to finally fix it once and for all, and got the motivation to do it after the ex/in gasket gave up a few weeks ago.

So what I did was source a section of 2" inside diameter pipe adapter from Advance, cut a piece about 2" long (1" in the manifold, 1" into the exhaust pipe), and chamfered the inside edges to eliminate sharp edges. This fit very snug using a hammer and flat plate of steel to drive it home into the manifold opening (I had previously honed out my manifold to about 2 1/4" diameter during my rebuild). I have 2 1/4" exhuast pipe, and just tapered the inside of it so the adapter fit snug into that......the adapter has no chance of going anywhere but a miniscule amount as the tapers in the manifold and exhaust pipe prevent moving much either way during any expansion.

What this will ultimately do is remove/limit any direct exhaust heat and pressure from the gasket.

So far so good. Easy to do if replacing the in/ex gasket. Pretty cheap fix, and no more dogpile sounding vehicle.
I'll see how long it lasts and if there are any unintended consequences down the road with that piece in there.
Here's some pics: