You can go a little more on cam. 236 @ .050 won't hurt. No more the 72 degrees of overlap.
Unfortunately though the C is one of the most sensitive engines I've ever seen, to compression ration and gas octane. If you keep it under 10.5:1 you should be ok.
If you go too much under that, the engine is a dog. Slugish. If you go over it is an animal but you will need leaded racing gas. None of this unleaded crap.
It really is too bad that this engine likes 11.5:1 so much. Likes is an understatement. It loves it, but you would need old Sunoco 260 to run it.
As it is, you need to run the stock heavy distributor advance springs to slow the advance curve.
Also be aware that there are almost no intake manifolds that will fit under the stock screen. The Blue Thunder Pantera manifold is nice but it is a big port.
As George says, 400hp is easy. 500 is right there if you want to put up with a little BS now and then?