If I pull a barrel off a left-hand Model 70 action, are the threads and extractor groove such that it can be fit to a right-hand action?

I really don’t know; seems from a manufacturing perspective it would make sense, but I’m not a smith.

Threads are right hand regardless. If the extractor cut lines up the lettering on the barrel will be upside down.

And I'm highly doubtful they'll line up with the barrel on tight.. I've never had a LH go to RH (or vice-versa) and had it go on without machining for either the extractor cutout and headspace aligning.. ... ..

Would it even be worth messing with...assuming I’m willing to pay for the machining, or would I be money ahead to just buy a new barrel?

Buy a new barrel, don't phuque around with a cheap (ER Shaw) barrel, you won't be disappointed

THAT!

This is a factory barrel, but thanks.

A better barrel will be worth it, sell the take off.