1st Floor: 80mbtu heat, 36mbtu sensible heat
2nd Floor: 45mbtu heat, 31mbtu sensible heat
1st floor requires 4-ton ac, which requires 1600cfm blower
2nd floor requires 3.5-ton to reach sensible heat. The 60mbtu furnaces have 1200cfm blowers restricting them to only some 3.5-ton units.
For the 1st floor
Some brands (such as Rheem, Lennox, Goodman) have 90mbtu furnaces that handle the second floor with a small margin. Others have very high efficiency (such as York-98, Nordyne-97) that undersize just a little, with in the calculation error. Others (such as Trane) don't offer as 1600cfm blower in an 80mbtu furnace, requiring a 100mbtu model.
On the 2nd floor, most manufactures have a 14-15 SEER single-stage 3.5 ton AC that can be used in the 60mbtu furnace. However, they differ significantly. Carrier has numerous models with 17-18.5 SEER in there 60mbtu ICS furnace. Others offer models that only obtain 13 SEER using a flat coil.
Do the specific Manual J requirements favor one brand over another and leave others, for example Trane in this case, inappropriate because a furnace/ac combination can't be reached that has appropriate sizing for each?