He beats the first two comfortably (although Casamayor could make it awkward for a few rounds, the man was skilled but not to anywhere near Floyds level). Forrest could be very interesting. A 6ft tall, rangy sharpshooting guy with good handspeed and power and an aggressive streak. I can't think of too many fighters like that on Floyds record. I'd lean towards Floyd to get the job done but he'd be genuinely tested here.
What about Spinks? Floyd certainly never fought anyone even remotely close to Spinks defense first style
Spinks could make for an awfully tedious fight with two defense first fighters meeting. But Floyd has big advantages in punch varieties and hand speed in my view plus is better defensively as well. And for one of the rare times above 130 Floyd would be the bigger puncher in there. That would be enough for him to take a clear UD or maybe late round stoppage in my opinion.