IMHO the 261 cam is too quiet, but it does offer an advantage: the likelihood of extensive jetting mods is much reduced (compared to a hotter cam).
More overlap and later intake closing changes the vacuum characteristics of the engine, which affects low speed mixture quickly.
The internal passages in the intake manifold is a terrible "S" curve (Brits call this a "swan neck"), done for space considerations. I would be temped to blend and radius every shape change or interruption I could reach, but there's no way to insure doing all three the same.
I would definitely port the interior of the exhaust manifolds, beginning with matching the flange openings to a new exhaust gasket.
