Thanks for the replies. Yes the flywheel is held on by 6 bolts, so initially it looks like I was off by a bolt. However there is also a dot on the crank pulley, and it's off by 60 degrees too! I haven't messed with the crank sprocket, so either the factory or a PO put it on wrong... or it's not a timing mark at all and is just a pulley alignment bump (the V-belt crank pulley has a corresponding bump).
I did put the belt on last night with TDC according to the crank not the flywheel, and turn the engine over slowly by hand. The valves are not hitting the pistons (and they will if you're off on the timing belt by even a little bit) so hopefully that is a good sign.
I actually drove the car for a few dozen miles after the clutch replacement before it overheated and blew the head gasket, so I didn't notice any severe vibration issues (though, as sdlomi2 mentions, they do normally vibrate a lot).
I used some white-out on the "new" TDC so hopefully that will last until the next clutch job.
Thanks again for the replies. This car has just been one challenge after another. :-/