If you have access to a valve spring tester then I would shoot for between 140 to 160 Lbs. on the seats and from 325 to 360 lbs. opened on a flat tappet or hydraulic flat tappet cam and lifters and at least have .060 to coil bind on all 16 springs. I shoot for + or - 5Lbs. on the seats, IE 140 to 150 lbs. on all 16 and use shims to get those results
Make sure on your coil bind clearances, it is far better to have .150 from coil bind at full open than to have .050 from coil bind at max lift
the last set of stock iron heads I set up for a local customer I had to grind some of his darn dampeners to get .060+ from coil bind on a mild hydraulic cam with .545 projected net lift, I told him to use a set of solid lifters with soft checking springs on all 16 valves and make sure and measure the net lift at the retainers to insure he wasn't within .060 from coil bind on all 16 springs
A iron block with iron heads will see a small net gain in lift once it is warmed up or running at or above 160 F