Big old house, had twin GEs, in horrid condition. Been trying to get him to boot them for years. Finally fan motor went out of one and the tech finally did. But they ran with 1 furnace and blower for a month in some cold weather. Had a 1" 16x25 above the old water wash EAC. 2 2.5 ton A/Cs in the plenum.
Old furnaces 108K 3 ton drive each
Metal design was my doings, had the "drop" made then installers ran the ducts to the furnace. Would have preferred 2 bears but wasn't sure how to do it neatly and without taking up much more room. We is moving some good air anyway. Airflow out of the registers is stronger than with the twins.
Tappan 95% 2 stage variable speed blower 120K
Using IAQ to control the 2 stage heat and also am staging the A/C bring 1 on first and the other as 2nd stage just to see how that works at making the temps more even.