Converting old toilet location to drain for new toilet n shower using raised floor

[John Little]

I'm a novice but capable of following directions.

Situation:

• Old bathroom in a garage with concrete slab.
• I demo'd the old bathroom, framed the walls to the new bathroom.
• Shower and toilet are at new locations.
• I'm using a 2x8 treated raised floor to run the plumbing.

Questions:

1. What is the most efficient way to connect the 3" toilet drain and the 2" shower drain in to the old toilet drain?Also plumbing the washing machine into the same system - putting P-trap in wall on upstream side of shower.

My novice plan - cutting the old flange out and chipping/cutting the concrete down below the flange connect and making enough room to install a 3" coupler and then a 3" - 90 w/a 2" inlet.

There's not alot of room below the flange before an elbow/90 turns.

I noticed at big box stores they have a twist in toilet flange.

2. Is there a "twist in" 90 or other to connect into the existing 3" sewer system?

Thanks for any help you can give me.

John