318 LA rebuild after losing a valve seat

Rather than putting time and focus on changing springs for break-in for something like a 901 spring, the OP's time and focus is far better spent on:

• When the engine is assembled but before the intake is on, prime the engine
• Then put marks on the pushrods and lifters, and rotate the engine it several times by hand to make sure each lifter rotates, at least a little bit. Lack of lifter rotation will kill a cam lobe even with stock springs!
• Make sure that a good moly cam lobe paste (like Isky cam lube) has been used between lifters and cam lobes, not a runny cam break-in fluid