Get the proper gasket with the block off...
If you use the wrong material, it will burn through...
Even with the right material it may also if not installed correctly...
We put an engine on a dyno with one exhaust crossover flange gasket torqued properly, and one that wasn't... The one that wasn't torqued properly burned through, the one that was didn't... That proved that you had to have the joint tightened properly for the gasket to survive that heat/environment, even with the proper material...