I started a new post as the old one was mis-titled.

I'm adding a bathroom and need help running the DWV lines. I went under the house today to hook up the hot/cold supply for this new bathroom. I noticed that the current setup (built in '71) for the bathroom is as follows:

The main CI line 4" comes from the tank and goes straight up through the roof to vent (3" vent). Below the bathroom floor is a 4-way connection to this waste/main vent line (each connection is @ 90 degees). Two toilets dump into this @ 180 degrees of each other (back-to-back on opposite sides of the wall). 90 degrees from the toilets one bathtub is plumbed in. 180 degrees from this bathtub (or 90 from each toilet) a single line in plumbed which combines: 1 bathub, laundry, and kitchen. At about 24" above the floor (approx) each sink dumps into this vent stack. None of the bathroom items have additional vents, and they are all well within 5' of this 3" line (probably at most 3').

Noticing this, I am assuming that the drawing below would be correct as it mimicks the current setup that I have. Would this be a correct assumption? What was code 30 years ago may not be code today...

I am assuming that the shower and lavatory do not need additional venting as they are within the 5' requirement for a 2" fixture arm.

Or would something like this be more appropriate?

Any help here would be appreciated...