On a 350 c.i engine the AFR 185's can support upto about 560 hp.
(est. hp based on airflow = .2575 x CFM x # of cylinders)
Using this as a guide, you'll need about 220 cfm of airflow per cylinder to support 450 hp. (I assume this is in a highly tuned state)
If you can find flowbench numbers for intake manifolds, you'll want something that can flow about that per runner (or better yet within 10% of the intake port, I assume on the high side? So more like 110%). The info I have handy on intakes is very sketchy (wish I had some old Super Ford magazines handy
)
Most if not all of the aftermarket heads can get you there without porting. However if you can get an improvement in the quality of airflow (not nessecarily more CFM), or improve the combustion dynamics via porting then go for it.