Meaning, the factory plug wire heat shields that are secured by the lower head bolts.

Looking at a car that's missing them from an engine rebuild many years ago.
Wondering if loosening a few of the bottom head bolts to install the shields is asking for grief...
Odds are, this would be done with the engine in the car if possible.

Well, then - 100 + views and no reply tells me it's not a good idea...

I don't think it would hurt anything. Especially if it has typical head gaskets...not a multilayer steel or copper.

I would do it cold though, not a tiny bit warm

Thanks, guys - I don't know what head gaskets the thing has, was done a LONG time ago.
Allegedly very few miles since it was blueprinted when new.
What looks like the edge of the HG has acquired the same appearance as the side of the block where the paint has worn off (which seems odd).
I would guess OEM steel, possibly the thin MP type.

I have done it on engines with both composite and steel shim gaskets without issue. I'm not sure why it wouldn't work on an MLS gasket also. Most recently I added the spark plug wire holders on the low deck in my Dart. No issues and dry as a bone.

If there is a small leak in any case a few tabs or bottle of stop leak will take care of it. If the engine coolant passages are clean/dry I have had amazing luck with Moroso Ceramic Seal. We had an external leak on a 2.2L TT2 engine and it was bad. Followed the directions loosely (cooling system was flushed and dry but it had antifreeze previuosly) and it never had an issue again. I was shocked.