340 Head gasket

I think you’re running into “trying to get back to 10.5” it probably never was 10.5, higher that other LA’s? Yes, true 10.5 probably not. The deck heights are usually higher than spec. How far in the hole are your pistons. I would lean towards the cometics. Probably overkill, but the lack of a 5th head bolt needs all the help it can get. As long as the surface finish is to the spec. I just search for a conversion for RA to sandpaper grit. To give me an idea of how smooth it needs to be. It isn’t THAT smooth.