I'm not knowledgeable of your Olds heads, but it would seem that you can run whatever spring you want with proper machining and setup.
Regarding valve float and understanding that repeated valve float is bad : you mentioned previously 'The heads have about 20k miles over 18ish years, I suppose.' Were those the original springs? If they were and you were street driving this only, then OK. Spirited driving is one thing, but drag racing is another - the hotter the oil, then less cooling of the springs - many things are better hot - valve springs aren't one of them 😉 .
Without knowing your lifter, pushrod, valve and spring retainer weights, it would be difficult to guess at a spring. The combination that 500/600 described above of 140ish seat and 360ish nose pressure seem fine to me. But his cam has a fair amount more lift than yours, implying your nose pressure will be much less implying you could possibly be floating valves at a lower rpm than he is with more lift. There are people that know these things precisely (I'm not one of them). Personally, I prefer Pac springs and the people at Pac - I'm yet to hear of anyone that has been lead astray by their advice or their springs. And they are easy to talk to and contact, or I should say they were pre-Covid at least.
Something to keep in mind about beehives, they will not have the life expectancy of a double spring. But they are cheaper to replace. The goto sloppy turbo LS spring is the Pac 1218 beehive. They work great when new, but most of these builds don't see 10 years and many of them don't make it 10 months lol. The 1218's new are holding fast for me so far at 22psi and 7500 rpm's with .585 lift, but I expect to be replacing them some time next year if the heads are still one piece by then.
I recommend contacting either a spring manufacturer or a known cam grinder, i.e. Mike Jones, Chris Straub, etc.
My two cents - Jim
