This engine will be fun! A couple of things-
Unless there's something about the aluminum cases I don't know about, stock oil control and oil relief springs are fine; as a matter of fact, a stronger spring at the flywheel end will blow up the cooler.
Are you going to be using Scat lifters as well? They have a reputation of not lasting very long. Send them to Steve Long for his treatment (I don't know what it is).
What length gears are in the oil pump? Any thing bigger than 26mm and you're wasting power by continuously pumping the extra oil back into the sump. I've never liked the Melling pumps- the cast iron bodies don't expand with the case as the engine heats up and sometimes they are the source of lower oil pressures at idle when hot.
I would use the type 1 sled tins, bottom diverters and industial tins; they were made for the upright cooling configuration. The sled tins also protect the cylinder bottoms and the thermostat from colder air (and water) while the car is moving.
Do you mean C35? C25? C45? Engle W120?
I know they are more money, but Aircooled.net's aluminum pushrods are easier on the valve train (because they are lighter), their expansion characteristics match the engine better, and you may find the chromoly ones are noisier when the engine is up to operating temps.
If you're buying rockers, buy 1.25's; they'll give close to 1/2" lift with the cam you're looking at, which is perfect for those heads. Anything less is leaving power on the table.
You could bump up the compression a 1/4 or 1/2 point (depending on the cam).
PS- A magnesium case would be perfectly adequate for this build.
PPSS- Consider modifying the engine case, followers and rockers for better oiling-