I actually got a contractor out to cut the hole for the tank. I was planning on a 7'8", but it turned out I was only able to have a 6'10" because of stupid support beam(made up of 6x 2"x6") holding up the garage. For a second I was thinking about moving the beam, until the contractor gave me a quote of $2,500. Then suddenly the 6'10" seem plenty.. 
He also installed 12" LVL header, but that wasn't necessary because all the weight was bearing down on the support beam.
Here is couple of pics.
Hole in the wall from the garage side.
Pic of the hole from the dinning room.

He also installed 12" LVL header, but that wasn't necessary because all the weight was bearing down on the support beam.
Here is couple of pics.
Hole in the wall from the garage side.

Pic of the hole from the dinning room.
