Add vents to these vanities?

I'm embarking on a total re-do of my bathroom. House built in 1961 and all fixtures and plumbing are original.

The waste drains are all galvanized steel which I will change to PVC. I am also moving them slightly to accommodate the new vanity. As I suspected, they are not vented individually, but rely on the vent in the wall behind the toilet, which ties in to the cast iron stack in the basement. The sinks are 36" part, and the closest sink is about 30" from the vent. New position will be about 4-6" closer to the vent, so when done a total of 5' (give or take) from the existing vent.

Should I open up more of the wall and tie them into the vent behind the toilet? They drain fine as is, but since everything is opened up I don't mind going the extra mile here. I know the vents will need to be at least 6" higher than the vanity's overflow, and should slope back toward the drain slightly to allow condensation or rain to drain away.

Current galvanized pipe is 1.5". Vents should also be 1.5 until it meets the existing vent, correct? (Toilet vent is 3" I believe.)