I helped do one of these in NY a few years back
We used 3" for the toilet (code minimum everywhere, I think).
The shower was on a 2" (that's the size you need for the drain connection anyways, and I think it was code as well)
The sink on 1 1/2, drained into the shower drain, though.
Backvented the sink and the shower individually.
That was a nasty, scary gig. Old tenements are the worst. The stack (3 stories, cast-iron) was running up a little lightwell (maybe 3' x 4', with a vented skylight at the top, windows to each apartment, relic of the earliest ventilation codes). No supports or brackets or anything, all the way up. Braced only by the drain & vent lines coming from the apartments on each floor, and held up by... the compressive strength of the cast-iron below... which I was about to cut. I had the chain cutter in hand, literally, when I happened to look up through a hole in the floor above.
Luckily each apartment also had a window to the lightwell (most had been painted shut for decades), because it was way too small to set a ladder in. We spent 3 days installing braces for pipe brackets across in the lightwell to hold up the stack, and I was still scared spitless when I cut that pipe...