If it were I, I'd get new pistons and rods. For 350's at least pistons are cheap (as long as you aren't talking forged) and newer rods are better/stronger pieces to. For a motor that will see high RPM use, I'd definitely want the "insurance" of better parts.
As to the heads, I'd go with something that flows well. Maybe not too outrageous, but since the power in those motors is all up top, you don't want something that flows good at low end and poor up top.
My take anyways...I had dreams of building up a 302 once.

Great novelty motor, but in my case I just decided the better overall performance of the 350 was the way to go. Be interesting to see how you like it once its all together.