So with the dash out it made sense to also pull and contemplate a heater box overhaul as well.
So I pulled it from the car today. Fairly easy qty 2 11mm on the bulkhead and two clamps to detach the hoses.
Set it down and cleared away the discintegrated 50 year old foam.
As others have warned...there is still antifreeze in the unit!
I layed down some linoleum on the passenger side floor and tilted it out to that side.... sure enough.
If your doing this job as well have rags/ paper towels handy.
Variety of pics below.