You don't need to rebuild the top-end to replace pushrod tube seals, in fact some people don't even undo the two nuts securing the head to the cylinder when they replace them, just the 4 rocker arm nuts that secure everything to the engine studs. I didn't follow this thread from the beginning, so maybe there's a reason to rebuild, but definitely not just for leaky pushrod tube seals.

bike's looking good though, keep it up