Will my Dynaco MKII power My Magnepan MGII's?

Power them, yes. Sound good, doubtful. If you're in a small room listening nearfield it may sound ok but, Maggies like power and current...the more the merrier!!!

"My Dynaco MK II" means you already own it. Try it. What do you think?

Good answer, Eldartford:
Try it! What a concept. I drove Maggies, some MG1s (ancient history) with about 80/side and it worked fine, until I got to a larger room with more demands. Than it simply ran out of steam. Likewise, some 1.6s with a Roten RB-1070 which doesn't even have a specified 4ohm output. Even though the rotel is pretty buff, for it's 130x2 (@8) it didn't have the grunt. 5000 cubic foot room....

You have both? I gotta ask, "why don't you hook them up and see for yourself?"

You need more horsepower.