remove the exhaust manifold?

Yep, I remember those, so the tubes for the air injection are long to get near the exhaust port output. I would use WD40 and let it sit. Then use a slide hammer to help pull the tubes from the manifold. Please let us know what happens.

Thank you for the advice. I didn't realize these small threaded tubes are supposed to detach after loosening the outer nuts. I'll give them some oil like you suggested and then loosen all four in hopes that maybe they'll slide apart by hand. This image shows what I'm intending to do with an arrow. It will take me about a week to get back to this, and I'll report on the results.

Yep, you are headed in the right direction, please let me know how it goes.

Well, I got some oil into those hex nuts and tube connections, let them sit like you mentioned and then after loosening the final one they all slipped right apart. The hard part was removing the lower bracket with four bolts for holding the metal tubes in place. I oiled them but stripped one with an open side wrench then finally got it loosened with a socket. Tapped the others with a hammer and closed side wrench to get them freed up.

If I'm able to get the rest of it disassembled, do you have a recommendation of what the best thing is to use for cleaning off the old head gasket material? I'd like to make it shine but don't know what will work without leaving scratches.

Nice work. For gasket removal I use a gasket scraper and a gasket gun.

https://amzn.to/3sEYBGe

Check out the link above.

I appreciate your suggestion, it worked very well.

The engine is mostly back together now, but I found that a bolt for fastening the front pipe brace took the first few threads out of the hole and won't reach any further. The hole has about an inch of good threads left, so I guess it's a matter of using a longer generic type of bolt. Do you know what thread size this takes? The bolt has a "9" on top, and the replacement bolt part number appears to be 9979-40-816. The way it fits is shown in the attachment 'front-pipe-brace.jpg'.

Also, there was a black wire attached to a small black box on the distributor from the ignition coil that got disconnected with no wire left to rejoin it. The black box has a metal tab screwed onto the distributor, so I wonder if this is a gound connection for the ignition coil. Do you know how to fix this? I can't find a replacement for the black box, and don't know how else to connect the wire.

I believe the thread size it 8mm x 1.50, but you can take one of the other bolts to match it up, also the black wire to the small black box is for a noise suppressor to help the radio so I don't think you need to worry about it unless the radio starts making noise.