How much would 404s and springs effect a b20

i just baught a b20b head. and im planning on getting the block soon but in teh meantime i was thinking about buildin up the head

i found crower 404’s with 4,000 miles for $210
and web cam valve springs for $120

would it be worth puttin these in and what kinda gains would i havbe with them and say titanium retainers…? witha stock bottom end?