Just spent about two hours chopping the heads from eight Revell 1/72 Austrian fusiliers in the kneeling position and attaching them to the bodies of eight Zvezda Saxon Napoleonic Cuirassiers. I used my pin vise to drill holes into the necks and heads followed by bits of staples to pin each head to its new body. Once I was sure everything would fit, I finished by cementing the joints with Plastic CA, a thin cyanoacrylate glue made for gluing soft plastics together.
The joints look pretty good and the glue seems to fill in any small gaps. I ended up using Austrian heads because they are somewhat bigger than the Prussian musketeer heads that I originally planned on. The Zvezda figures are BIG heavy cavalry figures, and they needed heads that would not look out of place on their bodies. I'm pleased with my first ever attempts at figure conversions. Just call me "Victor"!