The thing to consider with springs is how much rpm and how much boost are you gonna run.
I've used the crow kit with retainers up to 40psi which is probably too much spring for a 20psi tune...but not the worst.
Have a look around and see what they're rated for, ie how much seat pressure they have, then decide upon that.
You could consider our engines undersprung once they're tuned, the springs aren't stiff enough to close the valves in time. Conversely you don't want to run a super heavy spring if you don't need to cos it'll wear the valve train prematurely.
So yeah have a look, find some options then post again and get some feedback from others experience.