The iron heads are just fine, even better in some cases. Notice I said 'iron,' NOT stock. With a stock head, you'll have to put in hardened valve seats to protect against cracking. But the RHS or EQ heads are pretty dang good (especially for the price), and flow at least as much as the Edelbrock alum heads.
Geezzer, I am running the stock flexplate because it's balancing up to a 318 904 torque converter. I am balancing the dampner with the flexplate, and leaving the TQ unbalanced. So it doesn't matter which hole in the stock flexplate you file?