It's been 20+ years since I had stock manifolds on the SS but IIRC the heat shields are riveted or spot welded on. You should be able to determine by looking at them. If either that could be drilled out/ground off. Re-attaching them though you would need to either spot weld or tap/thread the manifold if you could and use a screw
Given you won't see what they cover once they are i maybe wire brush clean as best you can and then paint both by masking off the other
I just restored my 67 Camaro heat shields and iron manifolds although those are separate pieces. The heat shields I used aluminum header paint and they look great and will certainly take the heat
The iron manifolds I used Cast Blast which is a spray on/bake in oven process and they turned out very good and so far exhibit no signs of color fatigue
Cast Blast is good for 1200 degrees. I bought it on Amazon for around $10. I can should do both manifolds
Thanks, @BALLSS . There are definitely drive screws involved (they're the things that look like rivets). I can replace the drive screws once they're out. I'm planning to blast the manifolds, paint them with Eastwood's High-Temp Coating, refinish the shields with high-temp aluminum paint, and then re-install the shields to get a "like new" appearance.