I just bought a M70 Classic Featherweight 308 at a gun show. Nice wood for a factory rifle, matt finish on the metal. This has a hooded front sight and a Williams rear sight. I have never seen a featherweight with sights. How common are irons on this model rifle?

In theory they don’t exist from the factory.

In "theory". Maybe a custom shop rifle? I know other rifles were rumored to have been made with irons, and then you have the naysayers.

The barrel is marked Winchester M70 SA 308 Win and underneath Made in New Haven Ct USA. The serial number has a G prefix if this helps at all.

I would like to find one with sights

And just to confirm, it is marked classic featherweight, and it is controlled round feed?

Yes that's correct

Then the overwhelming likelihood is that they were aftermarket.