My $0.02 ...

If you go with aftermarket rockers for your FE, use the rocker shafts from the same manufacturer. I have heard of (but haven't seen personally) clearance issues when mixing brand A rocker arms with brand B shafts.

If you are running a mild hydraulic cam, take a look at the roller tip cast rockers. I think Crane makes them.

Talk to your machinist and see what he thinks about having rocker shaft end stands installed to minimize shaft flexing.

You may want to consider swapping out the rocker shaft springs & washers for the shimmed solid spacers to help keep the rocker arms centered over the valve stem tips. (btw. FE's dont need pushrod guide plates installed)

With a center oiler block, it's usually a good idea to drop in some oil restrictors
into the heads before you bolt down the rocker assemblies. Some people use .090 Holley jets, others cut short pieces of SBF pushrods. The most precise way to control top end oiling is tap the oil passages and use the center drilled thread in plugs.