No plumber would recommend plumbing the two lavs that way.
We have gone over this many times on this site.
Cast iron fittings are availible at a plumbing supply, not a big box store.
I find it always easier to cut in cast iron with no-hub coupings then it is to use plastic fittings, which by the way are a different size on the OD.
Measure your cast, and if it's 4-1/8" OD, then you will need a cast iron x copper no-hub coupling. New cast iron fittings are 4-3/8".
And PVC is a little bigger then that.
We have gone over this many times on this site.
Cast iron fittings are availible at a plumbing supply, not a big box store.
I find it always easier to cut in cast iron with no-hub coupings then it is to use plastic fittings, which by the way are a different size on the OD.
Measure your cast, and if it's 4-1/8" OD, then you will need a cast iron x copper no-hub coupling. New cast iron fittings are 4-3/8".
And PVC is a little bigger then that.