No experience actually driving a K cam, but the specs suggest it would be hard to tell the difference between them. Practically the same cam. If you were a butt dyno extraordinaire you might be able to tell that the D is slightly sportier. But only by a mouse fart.
And I have put D cams in otherwise pretty stock B18's before, and they felt great. My PV's stock B18 was a real tractor motor, no upper RPM power at all. D cam swap and it was a lot more fun to drive. Swapped the single downpipe exhaust manifold for a double and it was even more fun.
Detonation resistance on ye olde fashioned chamber design is partly compression ratio (what you're going at there) and partly how well it's et up to take advantage of squish/quench. Carefully measure that piston/deck height at TDC and then get a HG of the correct thickness to put the head .032 - .036" above it. That violently snaps the burning mixture into the central 'bathtub' chamber as the piston hits TDC. The closer the piston gets to actually touching the head, the better the turbulence and this helps more fully burn the mixture, in a more controlled fashion, and helps reduce hot spots. The effect rapidly diminishes as the distance increases. To more precisely set it, I use Cometic MLS HG's, they don't compress at all, the thickness listed is the thickness installed.
That said, it is a steel head, and steel heads in general are a bit more prone to having hot spots and detonating, so even with good squish, maybe shoot for something under 10.5:1.
Lowering the CR with a thicker HG is initially not productive, because you lessen the squish, and only eventually gain back some detonation resistance through lowered CR.
EDIT: And of course, there's static CR - what the displacement vs. the volume of the chamber/cylinder walls/HG at TDC, and the dynamic CR - which involves when the intake valves actually close. The CR you can use with a given octane fuel varies depending on that, as well as the CR, as well as the carb mixture, as well as the amount of squish, spark plug temp range, phase of the moon, etc. Also, a little occasional light sprinkling of pinging isn't really a bad thing on an old motor, it's not like detonation happening under lots of boost. No ping-ping-boom on a NA Volvo OHV.