I like the Hughes spring and retainer kit. It is an easy drop-in setup, perfect for stock heads. You would run into retainer-to-guide clearance issues if the lift is much over about .540 advertised lift, or duration is really long, before that spring kit was an issue.
Do you mean the heads are going in to a machine shop for freshening? The cracks everyone talks about are usually between the two valves. They don't leak coolant, so nobody ever knows they are cracked until they get removed for a rebuild.
