Not sure about that so I don’t know. That area where the exhaust crosses over gets extremely hot. I mean real hot.
Any oil that hits it when it’s hot Coke’s off.
If you are even half careful you should be able to get them out. 99% of the time it’s pretty easy.
I have had a couple of times where I broke one off or the hole was so blown out no amount of peening would tighten up the hole and I would find another spot on the casting that would take a rivet and drill it there and put the rivet in.
You can get those rivets from Goodson IIRC or similar sources.
I think you’ll do just fine getting them out.