It’s real simple. Manufacturers lie.
No way would I put any spring in there that wasn’t 240 on the seat minimum and 280 would bother me if you bought Chrysler correct lifters.
What it is over the nose as long as it’s 650 or higher.
If you do not have lifters with at least an .800 diameter wheel STOP and buy them.
A .750 wheel is too small. That’s for Chevy garbage.
Low spring load will kill parts. High spring loads won’t.
Do not buy into the lie that spring pressure hurts parts. That straight bullshit.