This group sometimes reminds me of all the things I don't know!
Thanks for all the advice.

You need to specify the width of the house perpendicular to the wall,
and what is being supported by the wall. It sounds like the wall is
an interior bearing wall supporting the first floor ceiling joists and
the attic space above. Is that right?

Yes, that's right. The house is roughly 24' wide by 42' long, so the
width of the house perpendicular to the wall is 24' (ie, 12' on either
side) It's a bungalow, so only supporting an attic and roof (plus
snow load in the winter, I'm in Canada). Hopefully this makes some
sense?

I sounds like I should be okay with 2 2x10s plus 2 jack studs, and if
I use 2x12s, all the better. Does this sound right?