I just purchased a house with two gas furnaces serving two separate ventilation systems (the second serves additions on each end of my ranch 1820 sq. ft) with one central a/c unit connected to both systems with flow control units. All of the equipment is very old (approx. 25 years) The main lennox furnace is in excellent condition, but the second furnace a baby boy carrier and the carrier a/c is not very efficient.
Contractors are giving me different recommendations:

1.) Keep the full size lennox and replace the baby boy furnace with a new one, remove the flow controls (which they say is complicated), replace the a/c and let the new a/c flow freely into the two ventilation systems.

2.) The second contractor wants to remove both furnaces and replace them with one new high efficiency furnace connected to both ventilation systems (the farther one will have a bend to connect it), and a new a/c. I will then need to use the dampers to deal with the uneven flow between the two vent systems.

Ps. Any advice I would truly appreciate.

Regards,
Dave