Looks like .30-06 can be sized into .280 Remington.
That is if it doesn't bother you.
It can but the shoulder will have to move forward a little (fireform), off the top of my head I do not remember how much. But it can be done
Looked at the SAAMI headspace length 2.1042 for the 280 and 2.0526 for the 06 both where the neck is .375 diameter. The body of the 280 was lengthened enough to not allow a 280 round from being chambered in a 270 Win and fired. That is why the case will need fireforming. to headspace properly.