I pretty much recognized the gasket from the picture. Read the description.
LINK
Fel-Pro 8523PT-1 Fel-Pro Cylinder Head Gaskets - Free Shipping on All Orders @ JEGS
LINK
http://www.summitracing.com/parts/FEL-8523PT-1/
Compared to:
LINK
http://www.summitracing.com/parts/fel-1037/overview/make/chevrolet
There is a reason the cost twice as much.
It could have been worse. It could have been a $15.00 8180 PT2
Less than perfect decking, at that compression, with that gasket is certain failure. You get a machinist pushing the fly cutter on too much angle and it leaves a low area right down the center of the head and or block.
With that compression, and iron heads, you have to give the engine a fighting chance by having everything PERFECT.
Tune, machining, and materials. It didn't take much to blow that particular gasket out between the cylinders.