ISO - Duct Transition for New Furnace (Spring Valley)

I have a furnace that i am replacing.
I do NOT intend to replace the AC Evap.
Coil on the system.
THe current furnace is an extremely old (1975 according to the Serial Number) Furnace.
The new Furnace is NOT the same dimension, so the duct work will need to be altered and a transition made to adapt to the new furnace.
Additionally, the A Coil will need to be supported in the duct.